ARM: tegra: fix Kconfig warnings when !SMP

Fix:

warning: (ARCH_TEGRA_2x_SOC) selects ARM_ERRATA_754327 which has unmet direct dependencies (CPU_V7 && SMP)
warning: (ARCH_TEGRA_2x_SOC) selects ARM_ERRATA_742230 which has unmet direct dependencies (CPU_V7 && SMP)

by selecting options only if SMP.
Signed-off-by: Stephen Warren <swarren@nvidia.com>

arch/arm/mach-tegra/Kconfig

@@ -6,9 +6,9 @@ config ARCH_TEGRA_2x_SOC
 	bool "Enable support for Tegra20 family"
 	select ARCH_REQUIRE_GPIOLIB
 	select ARM_ERRATA_720789
-	select ARM_ERRATA_742230
+	select ARM_ERRATA_742230 if SMP
 	select ARM_ERRATA_751472
-	select ARM_ERRATA_754327
+	select ARM_ERRATA_754327 if SMP
 	select ARM_ERRATA_764369 if SMP
 	select ARM_GIC
 	select CPU_FREQ_TABLE if CPU_FREQ