drm/msm/hdmi: Simplify with dev_of_node()

drm/msm/hdmi: Simplify with dev_of_node()

Simplify chain of pointer dereferences with dev_of_node() which also
checks if 'dev' argument is non-NULL.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/711167/
Link: https://lore.kernel.org/r/20260311-drm-msm-hdmi-cleanup-v1-1-c5535245f6de@oss.qualcomm.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>