gpio: Update gfp/slab.h includes for rdc321x

Implicit slab.h inclusion via percpu.h is about to go away.  Make sure
gfp.h or slab.h is included as necessary.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
1 file changed