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>

arch/arm/mach-tegra/board.h

@@ -28,13 +28,6 @@
 void __init tegra_map_common_io(void);
 void __init tegra_init_irq(void);
 
-int __init tegra_powergate_init(void);
-#if defined(CONFIG_ARCH_TEGRA_2x_SOC) && defined(CONFIG_DEBUG_FS)
-int __init tegra_powergate_debugfs_init(void);
-#else
-static inline int tegra_powergate_debugfs_init(void) { return 0; }
-#endif
-
 void __init tegra_paz00_wifikill_init(void);
 
 #endif