memory: tegra: Fix KCONFIG variables for Tegra186 and Tegra194

Commit a127e690 ("memory: tegra: Add support for the Tegra194 memory
controller") and commit 4e04b886 ("memory: tegra: Only include
support for enabled SoCs") incorrectly added the KCONFIG variables
CONFIG_ARCH_TEGRA186_SOC and CONFIG_ARCH_TEGRA194_SOC to the Tegra EMC
driver. These KCONFIG variables do not exist and prevent the EMC driver
from being probed on Tegra186 and Tegra194. These KCONFIG variable
names are simply missing one underscore and so fix this by adding the
necessary underscore to the variable names.

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>