Fixes failure with 4096x1080 resolutions

[  284.315379] WARNING: CPU: 1 PID: 901 at drivers/gpu/drm/vc4/vc4_plane.c:981 vc4_plane_mode_set+0x1374/0x13c4
[  284.315385] Modules linked in: ir_rc5_decoder rpivid_hevc(C) bcm2835_codec(C) bcm2835_isp(C) bcm2835_mmal_vchiq(C) bcm2835_gpiomem v4l2_mem2mem videobuf2_dma_contig videobuf2_memops videobuf2_v4l2 videobuf2_common videodev mc cdc_acm xpad ir_rc6_decoder rc_rc6_mce gpio_ir_recv fuse
[  284.315509] CPU: 1 PID: 901 Comm: kodi.bin Tainted: G         C        5.10.7 #1
[  284.315514] Hardware name: BCM2711
[  284.315518] Backtrace:
[  284.315533] [<c0cc5ca0>] (dump_backtrace) from [<c0cc6014>] (show_stack+0x20/0x24)
[  284.315540]  r7:ffffffff r6:00000000 r5:68000013 r4:c18ecf1c
[  284.315549] [<c0cc5ff4>] (show_stack) from [<c0cca638>] (dump_stack+0xc4/0xf0)
[  284.315558] [<c0cca574>] (dump_stack) from [<c022314c>] (__warn+0xfc/0x158)
[  284.315564]  r9:00000000 r8:00000009 r7:000003d5 r6:00000009 r5:c08cc7dc r4:c0fd09b8
[  284.315572] [<c0223050>] (__warn) from [<c0cc67ec>] (warn_slowpath_fmt+0x74/0xe4)
[  284.315577]  r7:c08cc7dc r6:000003d5 r5:c0fd09b8 r4:00000000
[  284.315584] [<c0cc677c>] (warn_slowpath_fmt) from [<c08cc7dc>] (vc4_plane_mode_set+0x1374/0x13c4)
[  284.315589]  r8:00000000 r7:00000000 r6:00001000 r5:c404c600 r4:c2e34600
[  284.315596] [<c08cb468>] (vc4_plane_mode_set) from [<c08cc984>] (vc4_plane_atomic_check+0x40/0x1c0)
[  284.315601]  r10:00000001 r9:c2e34600 r8:c0e67068 r7:c0fc44e0 r6:c2ce3640 r5:c3d636c0
[  284.315605]  r4:c2e34600
[  284.315614] [<c08cc944>] (vc4_plane_atomic_check) from [<c0860504>] (drm_atomic_helper_check_planes+0xec/0x1ec)
[  284.315620]  r9:c2e34600 r8:c0e67068 r7:c0fc44e0 r6:c2ce3640 r5:c3d636c0 r4:00000006
[  284.315627] [<c0860418>] (drm_atomic_helper_check_planes) from [<c0860658>] (drm_atomic_helper_check+0x54/0x9c)
[  284.315633]  r9:c2e35400 r8:00000006 r7:00000000 r6:c2ba7800 r5:c3d636c0 r4:00000000
[  284.315641] [<c0860604>] (drm_atomic_helper_check) from [<c08b7ca8>] (vc4_atomic_check+0x25c/0x454)
[  284.315645]  r7:00000000 r6:c2ba7800 r5:00000001 r4:c3d636c0
[  284.315652] [<c08b7a4c>] (vc4_atomic_check) from [<c0881278>] (drm_atomic_check_only+0x5cc/0x7e0)
[  284.315658]  r10:c404c6c8 r9:ffffffff r8:c472c480 r7:00000003 r6:c3d636c0 r5:00000000
[  284.315662]  r4:0000003c r3:c08b7a4c
[  284.315670] [<c0880cac>] (drm_atomic_check_only) from [<c089ba60>] (drm_mode_atomic_ioctl+0x758/0xa7c)
[  284.315675]  r10:c3d46000 r9:c3d636c0 r8:c2ce8a70 r7:027e3a54 r6:00000043 r5:c1fbb800
[  284.315679]  r4:0281a858
[  284.315688] [<c089b308>] (drm_mode_atomic_ioctl) from [<c086e9f8>] (drm_ioctl_kernel+0xc4/0x108)
[  284.315693]  r10:c03864bc r9:c1fbb800 r8:c3d47e64 r7:c089b308 r6:00000002 r5:c2ba7800
[  284.315697]  r4:00000000
[  284.315705] [<c086e934>] (drm_ioctl_kernel) from [<c086ee28>] (drm_ioctl+0x1e8/0x3a0)
[  284.315711]  r9:c1fbb800 r8:000000bc r7:c3d47e64 r6:00000038 r5:c0e59570 r4:00000038
[  284.315719] [<c086ec40>] (drm_ioctl) from [<c041f354>] (sys_ioctl+0x35c/0x914)
[  284.315724]  r10:c2d08200 r9:00000000 r8:c36fa300 r7:befdd870 r6:c03864bc r5:c36fa301
[  284.315728]  r4:c03864bc
[  284.315735] [<c041eff8>] (sys_ioctl) from [<c0200040>] (ret_fast_syscall+0x0/0x28)
[  284.315739] Exception stack(0xc3d47fa8 to 0xc3d47ff0)
[  284.315745] 7fa0:                   027eb750 befdd870 00000000 c03864bc befdd870 00000000
[  284.315750] 7fc0: 027eb750 befdd870 c03864bc 00000036 027e3948 0281a640 0281a850 027e3a50
[  284.315756] 7fe0: b4b64100 befdd844 b4b5ba2c b49c994c
[  284.315762]  r10:00000036 r9:c3d46000 r8:c0200204 r7:00000036 r6:c03864bc r5:befdd870
[  284.315765]  r4:027eb750

Fixes: c54619b0 ("drm/vc4: Add support for the BCM2711 HVS5")
Signed-off-by: Dom Cobley <popcornmix@gmail.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Tested-By: Lucas Nussbaum <lucas@debian.org>
Tested-By: Ryutaroh Matsumoto <ryutaroh@ict.e.titech.ac.jp>
Link: https://patchwork.freedesktop.org/patch/msgid/20210121105759.1262699-2-maxime@cerno.tech