MAINTAINERS: update Documentation file entry of GPIO subsystem

Signed-off-by: NKukjin Kim <kgene.kim@samsung.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

MAINTAINERS

@@ -2808,7 +2808,7 @@ GPIO SUBSYSTEM
 M:	Grant Likely <grant.likely@secretlab.ca>
 S:	Maintained
 T:	git git://git.secretlab.ca/git/linux-2.6.git
-F:	Documentation/gpio/gpio.txt
+F:	Documentation/gpio.txt
 F:	drivers/gpio/
 F:	include/linux/gpio*