ARM: tegra: build powergate unconditionally

powergate functions are needed for tegra30 as well (see common.c), so
build it always. Fixes:

arch/arm/mach-tegra/built-in.o: In function `tegra30_init_early':
apbio.c:(.init.text+0x78): undefined reference to `tegra_powergate_init'

(using "allnoconfig" with tegra30 enabled)
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Stephen Warren <swarren@nvidia.com>

arch/arm/mach-tegra/Makefile

@@ -8,9 +8,9 @@ obj-y                                   += timer.o
 obj-y					+= fuse.o
 obj-y					+= pmc.o
 obj-y					+= flowctrl.o
+obj-y					+= powergate.o
 obj-$(CONFIG_CPU_IDLE)			+= cpuidle.o
 obj-$(CONFIG_CPU_IDLE)			+= sleep.o
-obj-$(CONFIG_ARCH_TEGRA_2x_SOC)		+= powergate.o
 obj-$(CONFIG_ARCH_TEGRA_2x_SOC)         += tegra2_clocks.o
 obj-$(CONFIG_ARCH_TEGRA_2x_SOC)		+= tegra2_emc.o
 obj-$(CONFIG_ARCH_TEGRA_3x_SOC)		+= board-dt-tegra30.o