ARM: dts: lager: Configure pull-up for SOFT_SW GPIO keys

The GPIO pins connected to the 4 Software Switches (SW2) do not have
external pull-up resistors, but rely on internal pull-ups being enabled.
Fortunately this is satisfied by the initial state of these pins.

Make this explicit by enabling bias-pull-up, to remove the dependency on
initial state and/or boot loader configuration.

Signed-off-by: Geert Uytterhoeven <[e-mail]>
Reviewed-by: Wolfram Sang <[e-mail]>
Tested-by: Wolfram Sang <[e-mail]>
Link: https://lore.kernel.org/r/9fae3[e-mail]

arch/arm/boot/dts/r8a7790-lager.dts

···
 	keyboard {
 		compatible = "gpio-keys";
 
+		pinctrl-0 = <&keyboard_pins>;
+		pinctrl-names = "default";
+
 		one {
 			linux,code = <KEY_1>;
 			label = "SW2-1";
···
 	sound_clk_pins: sound_clk {
 		groups = "audio_clk_a";
 		function = "audio_clk";
+	};
+
+	keyboard_pins: keyboard {
+		pins = "GP_1_14", "GP_1_24", "GP_1_26", "GP_1_28";
+		bias-pull-up;
 	};
 };