ARM: tegra: enable Atmel touchpad in defconfig

This driver is used on Venice2 for the touchpad.
Signed-off-by: Stephen Warren <swarren@nvidia.com>

arch/arm/configs/tegra_defconfig

@@ -123,6 +123,7 @@ CONFIG_KEYBOARD_TEGRA=y
 CONFIG_KEYBOARD_CROS_EC=y
 CONFIG_MOUSE_PS2_ELANTECH=y
 CONFIG_INPUT_TOUCHSCREEN=y
+CONFIG_TOUCHSCREEN_ATMEL_MXT=y
 CONFIG_TOUCHSCREEN_STMPE=y
 CONFIG_INPUT_MISC=y
 CONFIG_INPUT_MPU3050=y