drm/msm: drop msm_kms_funcs::get_format() callback

Now as all subdrivers were converted to use common database of formats,
drop the get_format() callback and use mdp_get_format() directly.

Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/590431/
Link: https://lore.kernel.org/r/20240420-dpu-format-v2-9-9e93226cbffd@linaro.org