mtd: small typo in Makefile

Cosmetic fix: the path in the Makefile is wrong
Signed-off-by: Matteo Croce <matteo@teknoraver.net>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/devices/Makefile

 #
-# linux/drivers/devices/Makefile
+# linux/drivers/mtd/devices/Makefile
 #
 
 obj-$(CONFIG_MTD_DOC2000)	+= doc2000.o