We must always register the DRM bridge, since zynqmp_dp_hpd_work_func
calls drm_bridge_hpd_notify, which in turn expects hpd_mutex to be
initialized. We do this before zynqmp_dpsub_drm_init since that calls
drm_bridge_attach. This fixes the following lockdep warning:

[   19.217084] ------------[ cut here ]------------
[   19.227530] DEBUG_LOCKS_WARN_ON(lock->magic != lock)
[   19.227768] WARNING: CPU: 0 PID: 140 at kernel/locking/mutex.c:582 __mutex_lock+0x4bc/0x550
[   19.241696] Modules linked in:
[   19.244937] CPU: 0 PID: 140 Comm: kworker/0:4 Not tainted 6.6.20+ #96
[   19.252046] Hardware name: xlnx,zynqmp (DT)
[   19.256421] Workqueue: events zynqmp_dp_hpd_work_func
[   19.261795] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[   19.269104] pc : __mutex_lock+0x4bc/0x550
[   19.273364] lr : __mutex_lock+0x4bc/0x550
[   19.277592] sp : ffffffc085c5bbe0
[   19.281066] x29: ffffffc085c5bbe0 x28: 0000000000000000 x27: ffffff88009417f8
[   19.288624] x26: ffffff8800941788 x25: ffffff8800020008 x24: ffffffc082aa3000
[   19.296227] x23: ffffffc080d90e3c x22: 0000000000000002 x21: 0000000000000000
[   19.303744] x20: 0000000000000000 x19: ffffff88002f5210 x18: 0000000000000000
[   19.311295] x17: 6c707369642e3030 x16: 3030613464662072 x15: 0720072007200720
[   19.318922] x14: 0000000000000000 x13: 284e4f5f4e524157 x12: 0000000000000001
[   19.326442] x11: 0001ffc085c5b940 x10: 0001ff88003f388b x9 : 0001ff88003f3888
[   19.334003] x8 : 0001ff88003f3888 x7 : 0000000000000000 x6 : 0000000000000000
[   19.341537] x5 : 0000000000000000 x4 : 0000000000001668 x3 : 0000000000000000
[   19.349054] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffffff88003f3880
[   19.356581] Call trace:
[   19.359160]  __mutex_lock+0x4bc/0x550
[   19.363032]  mutex_lock_nested+0x24/0x30
[   19.367187]  drm_bridge_hpd_notify+0x2c/0x6c
[   19.371698]  zynqmp_dp_hpd_work_func+0x44/0x54
[   19.376364]  process_one_work+0x3ac/0x988
[   19.380660]  worker_thread+0x398/0x694
[   19.384736]  kthread+0x1bc/0x1c0
[   19.388241]  ret_from_fork+0x10/0x20
[   19.392031] irq event stamp: 183
[   19.395450] hardirqs last  enabled at (183): [<ffffffc0800b9278>] finish_task_switch.isra.0+0xa8/0x2d4
[   19.405140] hardirqs last disabled at (182): [<ffffffc081ad3754>] __schedule+0x714/0xd04
[   19.413612] softirqs last  enabled at (114): [<ffffffc080133de8>] srcu_invoke_callbacks+0x158/0x23c
[   19.423128] softirqs last disabled at (110): [<ffffffc080133de8>] srcu_invoke_callbacks+0x158/0x23c
[   19.432614] ---[ end trace 0000000000000000 ]---

Fixes: eb2d64bf ("drm: xlnx: zynqmp_dpsub: Report HPD through the bridge")
Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240308204741.3631919-1-sean.anderson@linux.dev
(cherry picked from commit 61ba791c)
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>