ARM: dts: socfpga: Add a 3.3V fixed regulator node

Without the 3.3V regulator node, the SDMMC driver will give these warnings:

dw_mmc ff704000.dwmmc0: No vmmc regulator found
dw_mmc ff704000.dwmmc0: No vqmmc regulator found

This patch adds the regulator node, and points the SD/MMC to the regulator.

Signed-off-by: Dinh Nguyen <dinguyen@opensource.altera.com>
Reviewed-by: Doug Anderson <dianders@chromium.org>
---
v3: Rename nodes to have schematic-name_regulator and remove "boot-on" and
    "always-on"
v2: Move the regulator nodes to their respective board dts file and
    correctly rename them to match the schematic
diff --git a/arch/arm/boot/dts/socfpga_arria5.dtsi b/arch/arm/boot/dts/socfpga_arria5.dtsi
index 03e8268..1907cc6 100644
--- a/arch/arm/boot/dts/socfpga_arria5.dtsi
+++ b/arch/arm/boot/dts/socfpga_arria5.dtsi
@@ -29,7 +29,7 @@
 			};
 		};
 
-		dwmmc0@ff704000 {
+		mmc0: dwmmc0@ff704000 {
 			num-slots = <1>;
 			broken-cd;
 			bus-width = <4>;