drm/i915/gvt: use well wrapped set_mask_bits() instead of defining new one

Macro set_mask_bits() is ready for us, just invoke it and remove
our write_bits().

Signed-off-by: Du, Changbin <changbin.du@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
1 file changed