drm/i915/uc: Remove redundant GuC support checks

Since commit db81bc6e ("drm/i915/uc: Consider enable_guc
modparam during fw selection") we have started using firmware
status as main indicator of the GuC support. No need to use
same checks twice.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190804195052.31140-4-michal.wajdeczko@intel.com