drm/amd/display: perform a bounds check before filling dirty rectangles

Currently, it is possible for us to access memory that we shouldn't.
Since, we acquire (possibly dangling) pointers to dirty rectangles
before doing a bounds check to make sure we can actually accommodate the
number of dirty rectangles userspace has requested to fill. This issue
is especially evident if a compositor requests both MPO and damage clips
at the same time, in which case I have observed a soft-hang. So, to
avoid this issue, perform the bounds check before filling a single dirty
rectangle and WARN() about it, if it is ever attempted in
fill_dc_dirty_rect().

Cc: stable@vger.kernel.org # 6.1+
Fixes: 30ebe415 ("drm/amd/display: add FB_DAMAGE_CLIPS support")
Reviewed-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>