Input: gpio_keys - set input direction explicitly

Commit 700a38b2 ("Input: gpio_keys - switch to using generic device
properties") switched to use generic device properties for GPIO keys and
commit 5feeca3c ("Input: gpio_keys - add support for GPIO descriptors")
switched from legacy GPIO numbers to GPIO descriptors.

Previously devm_gpio_request_one was explicitly passed GPIOF_DIR_IN flag
to set the GPIO direction as input. However devm_get_gpiod_from_child
doesn't have such provisions and hence fwnode_get_named_gpiod can't set
it as input.

This breaks few platforms with the following error:
" gpiochip_lock_as_irq: tried to flag a GPIO set as output for IRQ
  unable to lock HW IRQ <n> for IRQ
  genirq: Failed to request resources for POWER (irq <x>) on irqchip
  gpio_keys: Unable to claim irq <x>; error -22
  gpio-keys: probe failed with error -22 "

This patch fixes the issue by setting input direction explicitly for
gpio lines described by generic properties.

Fixes: 700a38b2 ("Input: gpio_keys - switch to using generic device properties")
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>