ARM: tegra: defconfig updates

Add:
* RTC_DRV_TPS6586X to enable the RTC on many boards, such as Harmony
  and Ventana.
* POWER_RESET_GPIO to provide a power off driver for TrimSlice.
* Tegra KBC controller support, for Seaboard.
* Tegra high-speed UART driver, for Cardhu Bluetooth.
* kexec support.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>