ARM: tegra: export tegra_gpio_{en,dis}able

These two functions are used in drivers that can be
modules, so they need to be exported.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Alan Ott <alan@signal11.us>
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>