drm/i915/guc: Load GuC on Coffee Lake

Coffee Lake reuses Kabylake's GuC.

v2: Change Coffeelake to Coffee Lake

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Reviewed-by: Lukasz Fiedorowicz <lukasz.fiedorowicz@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1496965704-23610-1-git-send-email-anusha.srivatsa@intel.com