drm/msm/dpu: Fix allocation of RGB SSPPs without scaling

drm/msm/dpu: Fix allocation of RGB SSPPs without scaling

Due to condition in dpu_rm_reserve_sspp, RGB SSPPs are only tried when
scaling is requested, which prevents those SSPPs from being reserved if
we don't need scaling at all. Instead we should check if YUV support is
requested, since scaling on RGB SSPPs is optional and is not implemented
in driver yet.

Fixes: 774bcfb73176 ("drm/msm/dpu: add support for virtual planes")
Signed-off-by: Vladimir Lypak <vladimir.lypak@gmail.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/681914/
Link: https://lore.kernel.org/r/20251017-b4-dpu-fixes-v1-1-40ce5993eeb6@gmail.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>