watchdog: mtx1-wdt: request gpio before using it

commit 9b19d40a upstream.

Otherwise, the gpiolib autorequest feature will produce a WARN_ON():

WARNING: at drivers/gpio/gpiolib.c:101 0x8020ec6c()
autorequest GPIO-215
[...]

Signed-off-by: Florian Fainelli <florian@openwrt.org>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andi Kleen <ak@linux.intel.com>