ARM: dts: turris-omnia: Add GPIO key node for front button

ARM: dts: turris-omnia: Add GPIO key node for front button

Now that we have the MCU device-tree node, which acts as a GPIO
controller, add GPIO key node for the front button.

Signed-off-by: Marek Behún <kabel@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20240701113010.16447-9-kabel@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>