ARM: dts: at91: sama5d4_ma5d4evk: fix regulator names

vcc_mmc1_reg is a fixed regulators and doesn't need a reg property. Remove
its unit-address.

Solves:
Warning (unit_address_vs_reg): Node /fixedregulator@2 has a unit name, but no reg property
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

arch/arm/boot/dts/at91-sama5d4_ma5d4evk.dts

@@ -159,7 +159,7 @@ panel_input: endpoint@0 {
 		};
 	};
 
-	vcc_mmc1_reg: fixedregulator@2 {
+	vcc_mmc1_reg: fixedregulator_mmc1 {
 		compatible = "regulator-fixed";
 		gpio = <&pioE 17 GPIO_ACTIVE_LOW>;
 		regulator-name = "VDD MCI1";