Input: gpio_keys - add support for GPIO descriptors

[ Upstream commit 5feeca3c1e39c01f9ef5abc94dea94021ccf94fc ]

GPIO descriptors are the preferred way over legacy GPIO numbers
nowadays. Convert the driver to use GPIO descriptors internally but
still allow passing legacy GPIO numbers from platform data to support
existing platforms.

Based on commits 633a21d8 ("input: gpio_keys_polled: Add support
for GPIO descriptors") and 1ae5ddb6 ("Input: gpio_keys_polled -
request GPIO pin as input.").

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>