drm/i915/gt: Define guc firmware blob for older Cometlakes

When splitting the Coffeelake define to also identify Cometlakes, I
missed the double fw_def for Coffeelake. That is only newer Cometlakes
use the cml specific guc firmware, older Cometlakes should use kbl
firmware.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2859
Fixes: 5f4ae270

 ("drm/i915: Identify Cometlake platform")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: <stable@vger.kernel.org> # v5.9+
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201229120828.29931-1-chris@chris-wilson.co.uk