drm/i915/dsi: skip gpio element execution when not supported

drm/i915/dsi: skip gpio element execution when not supported

Skip v3 gpio element because the support is not there, and skip gpio
element on non-vlv because the sideband code is vlv specific.

v2: the gpio stuff is currently only supported on vlv (Ville)

Cc: [email protected]
Fixes: 2a33d93486f2 ("drm/i915/bios: add support for MIPI sequence block v3")
Reviewed-by: Ville Syrjälä <[email protected]>
Signed-off-by: Jani Nikula <[email protected]>
Link: http://patchwork.freedesktop.org/patch/msgid/[email protected]