MAINTAINERS: update USB EHCI platform pattern

Commit f3bc64d6 ("USB: EHCI: DT support for generic bus glue")
removed the ehci-vt8500.c file, update the file pattern to include
ehci-platform.c.
Signed-off-by: NJoe Perches <joe@perches.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

MAINTAINERS

@@ -1321,7 +1321,7 @@ F:	drivers/mmc/host/wmt-sdmmc.c
 F:	drivers/pwm/pwm-vt8500.c
 F:	drivers/rtc/rtc-vt8500.c
 F:	drivers/tty/serial/vt8500_serial.c
-F:	drivers/usb/host/ehci-vt8500.c
+F:	drivers/usb/host/ehci-platform.c
 F:	drivers/usb/host/uhci-platform.c
 F:	drivers/video/vt8500lcdfb.*
 F:	drivers/video/wm8505fb*