ARM: tegra: Update multi_v7_defconfig

Enable some options that have recently been enabled on Tegra platforms:

  * TOUCHSCREEN_WM97XX: touchscreen support on Toradex Colibri
  * SND_SOC_TEGRA_WM9712: audio support on Toradex Colibri

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