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/gpu/drm/tegra/sor.c b/drivers/gpu/drm/tegra/sor.c
index eafd0b8..7f8ca5d 100644
--- a/drivers/gpu/drm/tegra/sor.c
+++ b/drivers/gpu/drm/tegra/sor.c
@@ -12,7 +12,7 @@
 #include <linux/platform_device.h>
 #include <linux/reset.h>
 
-#include <soc/tegra/powergate.h>
+#include <soc/tegra/pmc.h>
 
 #include <drm/drm_dp_helper.h>