ARM: tegra: move <mach/powergate.h> to <linux/tegra-powergate.h>

This is required so that code such as Tegra's PCIe and clock drivers
can still access this header file once Tegra is converted to
multiplatform, and <mach/> no longer exists.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
diff --git a/arch/arm/mach-tegra/pcie.c b/arch/arm/mach-tegra/pcie.c
index b60165f..46144a1 100644
--- a/arch/arm/mach-tegra/pcie.c
+++ b/arch/arm/mach-tegra/pcie.c
@@ -34,12 +34,11 @@
 #include <linux/delay.h>
 #include <linux/export.h>
 #include <linux/clk/tegra.h>
+#include <linux/tegra-powergate.h>
 
 #include <asm/sizes.h>
 #include <asm/mach/pci.h>
 
-#include <mach/powergate.h>
-
 #include "board.h"
 #include "iomap.h"