drm/i915/dsi: add support for gpio elements on CHV

Add support for CHV gpio programming in DSI gpio elements.

v2: Overhaul macros according to Ville's review.

v3: Address Ville's review:
 - swap E and SE gpio ranges
 - add a note about max SE index
 - use GPO, not HIZ
 - swap cfg0 and cfg1

v4: fix port for dsi sequence versions 1 and 2

[Rewritten by Jani, based on earlier work by Yogesh and Deepak.]

Signed-off-by: Yogesh Mohan Marimuthu <yogesh.mohan.marimuthu@intel.com>
Signed-off-by: Deepak M <m.deepak@intel.com>
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/bdaaf9915a5005305b31bb26cf619a5a82472f2a.1461666263.git.jani.nikula@intel.com