mtd: update gfp/slab.h includes

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: NTejun Heo <tj@kernel.org>
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/mtdcore.c

@@ -21,6 +21,7 @@
 #include <linux/proc_fs.h>
 #include <linux/idr.h>
 #include <linux/backing-dev.h>
+#include <linux/gfp.h>
 
 #include <linux/mtd/mtd.h>
 

drivers/mtd/nand/mpc5121_nfc.c

@@ -27,6 +27,7 @@
 
 #include <linux/module.h>
 #include <linux/clk.h>
+#include <linux/gfp.h>
 #include <linux/delay.h>
 #include <linux/init.h>
 #include <linux/interrupt.h>

drivers/mtd/nand/r852.c

@@ -15,6 +15,7 @@
 #include <linux/pci.h>
 #include <linux/pci_ids.h>
 #include <linux/delay.h>
+#include <linux/slab.h>
 #include <asm/byteorder.h>
 #include <linux/sched.h>
 #include "sm_common.h"