ARM: rmobile: Fix eMMC signal voltage on ULCB

The eMMC is 1V8 device only and the signaling is always 1V8,
fix the DT for ULCB to describe the hardware correctly.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>

arch/arm/dts/ulcb.dtsi

@@ -247,7 +247,7 @@
 	sdhi2_pins: sd2 {
 		groups = "sdhi2_data8", "sdhi2_ctrl";
 		function = "sdhi2";
-		power-source = <3300>;
+		power-source = <1800>;
 	};
 
 	sdhi2_pins_uhs: sd2_uhs {