mtd: mxc_nand: Include linux/of.h header

'of_match_ptr' is defined in linux/of.h. Include it explicitly to
avoid build breakage in the future.
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/nand/mxc_nand.c

@@ -32,6 +32,7 @@
 #include <linux/io.h>
 #include <linux/irq.h>
 #include <linux/completion.h>
+#include <linux/of.h>
 #include <linux/of_device.h>
 #include <linux/of_mtd.h>