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>