drm/amd/display: Remove unneeded semicolon

./drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c:7431:3-4: Unneeded semicolon
./drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c:7485:4-5: Unneeded semicolon
./drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c:7489:3-4: Unneeded semicolon

Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=3635
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>