drm/komeda: Adds SMMU support

Adds iommu_connect and disconnect for SMMU support, and configures
TBU translation once SMMU has been attached to the display device.

Signed-off-by: Lowry Li (Arm Technology China) <lowry.li@arm.com>
[fixed checking of error code returned by dp_wait_cond() and removed
extraneous DRM_ERROR() calls]
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>