MTX build failure

[Ralf Baechle <ralf@linux-mips.org>]

  CC      drivers/input/keyboard/gpio_keys.o
/home/ralf/src/linux/linux-mips/drivers/input/keyboard/gpio_keys.c: In function 
‘gpio_keys_probe’:
/home/ralf/src/linux/linux-mips/drivers/input/keyboard/gpio_keys.c:123: error: 
implicit declaration of function ‘gpio_request’
/home/ralf/src/linux/linux-mips/drivers/input/keyboard/gpio_keys.c:135: error: 
implicit declaration of function ‘gpio_free’
make[5]: *** [drivers/input/keyboard/gpio_keys.o] Error 1
make[4]: *** [drivers/input/keyboard] Error 2
make[3]: *** [drivers/input] Error 2
make[2]: *** [drivers] Error 2
make[1]: *** [sub-make] Error 2

  Ralf