drm/amd/display: fix cursor offset on rotation 180

Cursor gets clipped off in the middle of the screen with hw rotation
180. Fix a miscalculation of cursor offset when it's placed near the
edges in the pipe split case.

Cursor bugs with hw rotation were reported on AMD issue tracker:
https://gitlab.freedesktop.org/drm/amd/-/issues/2247

The issues on rotation 270 was fixed by:
https://lore.kernel.org/amd-gfx/20221118125935.4013669-22-Brian.Chang@amd.com/
that partially addressed the rotation 180 too. So, this patch is the
final bits for rotation 180.

Reported-by: Xaver Hugl <xaver.hugl@gmail.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Fixes: 9d84c7ef

 ("drm/amd/display: Correct cursor position on horizontal mirror")
Signed-off-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org