drm/i915/dsi: add support for sequence block v3 gpio for VLV

Only support North Core (NC) GPIOs for now, and assume the vlv gpio
table only has NC GPIOs for now.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/d51c9479e8ef0b201452086870e7785928a86289.1461666263.git.jani.nikula@intel.com