drm/i915/cnl: LSPCON support is gen9+

There is no platform specific change needed for LSPCON
support on Cannonlake. So let's make it gen9+.

Cc: Shashank Sharma <shashank.sharma@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1497047175-27250-17-git-send-email-rodrigo.vivi@intel.com