arm: tegra: boards: fix pinmux of GMI_CS7

bug 1398378

Change-Id: I7f5de50a26366c00a8a2322e7ee4136a0e872016
Signed-off-by: Jay Cheng <jacheng@nvidia.com>
Reviewed-on: http://git-master/r/327276
(cherry picked from commit 9a119e5c05711e311f732f85abf231aa08de1d14)
Reviewed-on: http://git-master/r/328706
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Harry Hong <hhong@nvidia.com>
Tested-by: Harry Hong <hhong@nvidia.com>