drm/radeon: fix order of doing things in radeon_crtc_cursor_set

 if object pin or object lookup in radeon_cursor_set fail, the function
 could leave inconsistent mouse width and hight values in radeon_crtc
 fixed by moving cursor width and height assignments after all
 checks have passed

Signed-off-by: Ilija Hadzic <ihadzic@research.bell-labs.com>
Reviewed-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>