ARM: tegra: Fix can2 on Tegra30 Apalis

CAN2 currently fails on probe as follows:

mcp251x spi1.1: Probe failed, err=19

Fix this by enabling input on pin mux of resp. SPI4 pins.

Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Marcel Ziswiler <marcel@ziswiler.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>