ARM: tegra: fix pinctrl misconfiguration on Venice2

Other boards use PULL_NONE for their debug UART pins, and without this
change, the board doesn't accept any serial input.

Don't set the I2S port pins to tristate mode, or no audio signal will
be sent out.

Fixes: 605ae5804385 ("ARM: tegra: add default pinctrl nodes for Venice2")
Signed-off-by: Stephen Warren <swarren@nvidia.com>