GPIO: TPS65910: Move driver to drivers/gpio/

The GPIO driver should reside in drivers/gpio/ for better
organization.

Signed-off-by: Jorge Eduardo Candelaria <jedu@slimlogic.co.uk>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>