qed: Avoid implicit enum conversion in qed_roce_mode_to_flavor

Clang warns when one enumerated type is implicitly converted to another.

drivers/net/ethernet/qlogic/qed/qed_roce.c:153:12: warning: implicit
conversion from enumeration type 'enum roce_mode' to different
enumeration type 'enum roce_flavor' [-Wenum-conversion]
                flavor = ROCE_V2_IPV6;
                       ~ ^~~~~~~~~~~~
drivers/net/ethernet/qlogic/qed/qed_roce.c:156:12: warning: implicit
conversion from enumeration type 'enum roce_mode' to different
enumeration type 'enum roce_flavor' [-Wenum-conversion]
                flavor = MAX_ROCE_MODE;
                       ~ ^~~~~~~~~~~~~
2 warnings generated.

Use the appropriate values from the expected type, roce_flavor:

ROCE_V2_IPV6 = RROCE_IPV6 = 2
MAX_ROCE_MODE = MAX_ROCE_FLAVOR = 3

While we're add it, ditch the local variable flavor, we can just return
the value directly from the switch statement.

Link: ClangBuiltLinux/linux#125
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/qlogic/qed/qed_roce.c

@@ -140,23 +140,16 @@ static void qed_rdma_copy_gids(struct qed_rdma_qp *qp, __le32 *src_gid,
 
 static enum roce_flavor qed_roce_mode_to_flavor(enum roce_mode roce_mode)
 {
-	enum roce_flavor flavor;
-
 	switch (roce_mode) {
 	case ROCE_V1:
-		flavor = PLAIN_ROCE;
-		break;
+		return PLAIN_ROCE;
 	case ROCE_V2_IPV4:
-		flavor = RROCE_IPV4;
-		break;
+		return RROCE_IPV4;
 	case ROCE_V2_IPV6:
-		flavor = ROCE_V2_IPV6;
-		break;
+		return RROCE_IPV6;
 	default:
-		flavor = MAX_ROCE_MODE;
-		break;
+		return MAX_ROCE_FLAVOR;
 	}
-	return flavor;
 }
 
 static void qed_roce_free_cid_pair(struct qed_hwfn *p_hwfn, u16 cid)