ARM: dts: blanche: Configure pull-up for SOFT_SW and SW25 GPIO keys

The GPIO pins connected to the 4 Software Switches (SW2) and the second
Tact Switch (SW25) 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.

Note that the GPIO pin connected to the first Tact Switch (SW24) does
have an external pull-up resistor.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/011e4c461767f2dd690b655b3dd501eb554184c1.1619785905.git.geert+renesas@glider.be

arch/arm/boot/dts/r8a7792-blanche.dts

@@ -112,6 +112,9 @@ x2_clk: x2 {
 	keyboard {
 		compatible = "gpio-keys";
 
+		pinctrl-0 = <&keyboard_pins>;
+		pinctrl-names = "default";
+
 		key-1 {
 			linux,code = <KEY_1>;
 			label = "SW2-1";
@@ -235,6 +238,11 @@ du1_pins: du1 {
 		function = "du1";
 	};
 
+	keyboard_pins: keyboard {
+		pins = "GP_3_10", "GP_3_11", "GP_3_12", "GP_3_15", "GP_11_02";
+		bias-pull-up;
+	};
+
 	pmic_irq_pins: pmicirq {
 		groups = "intc_irq2";
 		function = "intc";