TPS65911: Add support for added GPIO lines

GPIO 1 to 8 are added for TPS65911 chip version. The gpio driver
now handles more than one gpio lines. Subsequent versions of the
chip family can add new GPIO lines with minimal driver changes.

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>