arm64: defconfig: Enable sdhci-tegra driver

This driver is used to service the SDHCI interfaces found on NVIDIA
tegra SoCs. Enabling it allows SD and eMMC cards to be used for the
root filesystem.
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm64/configs/defconfig

@@ -156,6 +156,7 @@ CONFIG_MMC=y
 CONFIG_MMC_ARMMMCI=y
 CONFIG_MMC_SDHCI=y
 CONFIG_MMC_SDHCI_PLTFM=y
+CONFIG_MMC_SDHCI_TEGRA=y
 CONFIG_MMC_SPI=y
 CONFIG_MMC_DW=y
 CONFIG_MMC_DW_IDMAC=y