ARM: tegra: Make pinmux.h standalone includible

This header file uses type definitions (u8, u32) from linux/types.h but
doesn't include it. If includes aren't carefully ordered this can cause
build failures.

Cc: Tom Warren <twarren@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>