Davinci: gpio - controller type support

This patch allows for gpio controllers that deviate from those found on
traditional davinci socs.  davinci_soc_info has an added field to indicate the
soc-specific gpio controller type.  The gpio initialization code then bails
out if necessary.

More elements (tnetv107x) to be added later into enum davinci_gpio_type.

Signed-off-by: Cyril Chemparathy <cyril@ti.com>
Tested-by: Sandeep Paulraj <s-paulraj@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>