MAINTAINERS: Update gianfar_ptp after renaming

Commit ec21e2ec36 ("freescale: Move the Freescale drivers") moved the
files, update the pattern.

Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

MAINTAINERS

@@ -5556,7 +5556,7 @@ S:	Maintained
 W:	http://linuxptp.sourceforge.net/
 F:	Documentation/ABI/testing/sysfs-ptp
 F:	Documentation/ptp/*
-F:	drivers/net/gianfar_ptp.c
+F:	drivers/net/ethernet/freescale/gianfar_ptp.c
 F:	drivers/net/phy/dp83640*
 F:	drivers/ptp/*
 F:	include/linux/ptp_cl*