ARM: tegra: Convert PMC to a driver

This commit converts the PMC support code to a platform driver. Because
the boot process needs to call into this driver very early, also set up
a minimal environment via an early initcall.

Signed-off-by: Thierry Reding <treding@nvidia.com>
diff --git a/drivers/soc/tegra/Makefile b/drivers/soc/tegra/Makefile
index db34987..cdaad9d 100644
--- a/drivers/soc/tegra/Makefile
+++ b/drivers/soc/tegra/Makefile
@@ -1,3 +1,4 @@
 obj-$(CONFIG_ARCH_TEGRA) += fuse/
 
 obj-$(CONFIG_ARCH_TEGRA) += common.o
+obj-$(CONFIG_ARCH_TEGRA) += pmc.o