drm/amd/display: use swap() in update_phy_id_mapping()

Use existing swap() function rather than duplicating its implementation.

./drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crc.c:185:47-48: WARNING opportunity for swap().
./drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crc.c:125:53-54: WARNING opportunity for swap().

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=12335


Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>