octeontx2-pf: Fix assigned error return value that is never used

Currently when the call to otx2_mbox_alloc_msg_cgx_mac_addr_update fails
the error return variable rc is being assigned -ENOMEM and does not
return early. rc is then re-assigned and the error case is not handled
correctly. Fix this by returning -ENOMEM rather than assigning rc.

Addresses-Coverity: ("Unused value")
Fixes: 79d2be38 ("octeontx2-pf: offload DMAC filters to CGX/RPM block")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/octeontx2/nic/otx2_dmac_flt.c

@@ -161,7 +161,7 @@ int otx2_dmacflt_update(struct otx2_nic *pf, u8 *mac, u8 bit_pos)
 
 	if (!req) {
 		mutex_unlock(&pf->mbox.lock);
-		rc = -ENOMEM;
+		return -ENOMEM;
 	}
 
 	ether_addr_copy(req->mac_addr, mac);