drm/amdgpu: fix IB alignment for UVD

BugLink: http://bugs.launchpad.net/bugs/1638267

commit c4795ca6 upstream.

According to the hw team, it should be 16, not 8.

Cc: Peter Fang <peter.fang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c

@@ -227,7 +227,7 @@ static int amdgpu_info_ioctl(struct drm_device *dev, void *data, struct drm_file
 			type = AMD_IP_BLOCK_TYPE_UVD;
 			ring_mask = adev->uvd.ring.ready ? 1 : 0;
 			ib_start_alignment = AMDGPU_GPU_PAGE_SIZE;
-			ib_size_alignment = 8;
+			ib_size_alignment = 16;
 			break;
 		case AMDGPU_HW_IP_VCE:
 			type = AMD_IP_BLOCK_TYPE_VCE;