drm/msm/dpu: add formats check for writeback encoder

In preparation for adding more formats to dpu writeback add
format validation to it to fail any unsupported formats.

changes in v4:
	- change the failure message of the API
	  drm_atomic_helper_check_wb_connector_state() to a generic
	  one in case it checks more errors later and moreoever it
	  already has debug message to indicate its failure
	- change the corresponding DPU_ERROR to DPU_DEBUG in-line with
	  other atomic_check failure messages

changes in v3:
	- rebase on top of msm-next
	- replace drm_atomic_helper_check_wb_encoder_state() with
	  drm_atomic_helper_check_wb_connector_state() due to the
	  rebase

changes in v2:
	- correct some grammar in the commit text

Fixes: d7d0e73f ("drm/msm/dpu: introduce the dpu_encoder_phys_* for writeback")
Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/571811/
Link: https://lore.kernel.org/r/20231212205254.12422-2-quic_abhinavk@quicinc.com


[DB: removed extra debug message]
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>