mtd: remove duplicated include from mtdcore.c

Remove duplicated include.
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Acked-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/mtdcore.c

@@ -37,7 +37,6 @@
 #include <linux/backing-dev.h>
 #include <linux/gfp.h>
 #include <linux/slab.h>
-#include <linux/major.h>
 
 #include <linux/mtd/mtd.h>
 #include <linux/mtd/partitions.h>