ARM: dts: exynos: Silence DP HPD pinctrl dtschema warning in Exynos5250 Spring

The pin configuration of Display Port HPD GPIO emds with '-gpio' which
confuses dtschema:

  arch/arm/boot/dts/exynos5250-spring.dt.yaml: pinctrl@11400000: dp-hpd-gpio:
    {'samsung,pins': ['gpc3-0'], ... 'samsung,pin-drv': [[0]], 'phandle': [[23]]} is not of type 'array'
    From schema: lib/python3.6/site-packages/dtschema/schemas/gpio/gpio-consumer.yaml
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200901075417.22481-11-krzk@kernel.org

arch/arm/boot/dts/exynos5250-spring.dts

@@ -457,7 +457,7 @@ s5m8767_dvs: s5m8767-dvs {
 		samsung,pin-drv = <EXYNOS4_PIN_DRV_LV1>;
 	};
 
-	dp_hpd_gpio: dp-hpd-gpio {
+	dp_hpd_gpio: dp-hpd {
 		samsung,pins = "gpc3-0";
 		samsung,pin-function = <EXYNOS_PIN_FUNC_INPUT>;
 		samsung,pin-pud = <EXYNOS_PIN_PULL_UP>;