drm/i915/guc: Use GUC prefix for CORE_FAMILY definitions

Almost all other GuC fw definitions are using GUC|guc prefix.
While around, in get_core_family() change explicit WARN into MISSING_CASE
as it looks more appropriate, since GuC support capability we are controlling
by intel_device_info.has_guc flag.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170404133836.125736-1-michal.wajdeczko@intel.com
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/i915/intel_guc_loader.c b/drivers/gpu/drm/i915/intel_guc_loader.c
index 8a1a023..2793c01 100644
--- a/drivers/gpu/drm/i915/intel_guc_loader.c
+++ b/drivers/gpu/drm/i915/intel_guc_loader.c
@@ -86,11 +86,11 @@ static u32 get_core_family(struct drm_i915_private *dev_priv)
 
 	switch (gen) {
 	case 9:
-		return GFXCORE_FAMILY_GEN9;
+		return GUC_CORE_FAMILY_GEN9;
 
 	default:
-		WARN(1, "GEN%d does not support GuC operation!\n", gen);
-		return GFXCORE_FAMILY_UNKNOWN;
+		MISSING_CASE(gen);
+		return GUC_CORE_FAMILY_UNKNOWN;
 	}
 }