board: grouper: convert ASUS Google Nexus 7 (2012) to use DM PMIC

Since required drivers were merged, we can safely clean up the
board and switch to DM based driver with device tree support.

Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
diff --git a/arch/arm/dts/tegra30-asus-nexus7-tilapia-E1565.dts b/arch/arm/dts/tegra30-asus-nexus7-tilapia-E1565.dts
index 89348fd..ef8b2b5 100644
--- a/arch/arm/dts/tegra30-asus-nexus7-tilapia-E1565.dts
+++ b/arch/arm/dts/tegra30-asus-nexus7-tilapia-E1565.dts
@@ -35,6 +35,7 @@
 					regulator-name = "vcore_emmc";
 					regulator-min-microvolt = <2850000>;
 					regulator-max-microvolt = <2850000>;
+					regulator-boot-on;
 				};
 			};
 		};