drm/i915/bios: interpret the i2c element

Add parsing of the i2c element, defined in MIPI sequence block v2. Drop
the status operation byte while at it, that does not exist.

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/d8a2998977feee2f5b5ad609aaca787adfb41479.1450702954.git.jani.nikula@intel.com