Without this option, kernel builds would fail, with
errors similar to:

hsmmc.c:50: undefined reference to `twl4030_get_gpio_datain'
hsmmc.c:82: undefined reference to `twl4030_free_gpio'
hsmmc.c:63: undefined reference to `twl4030_request_gpio'
hsmmc.c:67: undefined reference to `twl4030_set_gpio_debounce'
Signed-off-by: Sanjeev Premi <premi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>