soc/amd/cezanne/graphics: simplify map_oprom_vendev implementation

Phoenix' implementation of map_oprom_vendev uses this simplified
implementation, so port this back to Cezanne too.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: I0aa3a0fed37c6cba15a668ada639f5fd0c212d2f
Reviewed-on: https://review.coreboot.org/c/coreboot/+/73387
Reviewed-by: Fred Reitberger <reitbergerfred@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/amd/cezanne/graphics.c

@@ -6,14 +6,11 @@
 
 u32 map_oprom_vendev(u32 vendev)
 {
-	u32 new_vendev = vendev;
-
 	switch (vendev) {
 	case CEZANNE_VBIOS_VID_DID:
 	case BARCELO_VBIOS_VID_DID:
-		new_vendev = CEZANNE_VBIOS_VID_DID;
-		break;
+		return CEZANNE_VBIOS_VID_DID;
 	}
 
-	return new_vendev;
+	return vendev;
 }