ARM: tegra: fix-up definition by adding 'static'

Fix up the definition of the tegra_gpio enable/disable.

Change-Id: Id71242690efa3e5994a4b70089826f2b87997ece
Signed-off-by: Matt Pedro <mapedro@nvidia.com>
Reviewed-on: http://git-master/r/140036
Reviewed-by: Automatic_Commit_Validation_User