ipv6: Optmize translation between IPV6_PREFER_SRC_xxx and RT6_LOOKUP_F_xxx.

IPV6_PREFER_SRC_xxx definitions:
| #define IPV6_PREFER_SRC_TMP             0x0001
| #define IPV6_PREFER_SRC_PUBLIC          0x0002
| #define IPV6_PREFER_SRC_COA             0x0004

RT6_LOOKUP_F_xxx definitions:
| #define RT6_LOOKUP_F_SRCPREF_TMP        0x00000008
| #define RT6_LOOKUP_F_SRCPREF_PUBLIC     0x00000010
| #define RT6_LOOKUP_F_SRCPREF_COA        0x00000020

So, we can translate between these two groups by shift operation
instead of multiple 'if's.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index b08879e..52cd3ef 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -819,15 +819,8 @@
 
 	if (!ipv6_addr_any(&fl->fl6_src))
 		flags |= RT6_LOOKUP_F_HAS_SADDR;
-	else if (sk) {
-		unsigned int prefs = inet6_sk(sk)->srcprefs;
-		if (prefs & IPV6_PREFER_SRC_TMP)
-			flags |= RT6_LOOKUP_F_SRCPREF_TMP;
-		if (prefs & IPV6_PREFER_SRC_PUBLIC)
-			flags |= RT6_LOOKUP_F_SRCPREF_PUBLIC;
-		if (prefs & IPV6_PREFER_SRC_COA)
-			flags |= RT6_LOOKUP_F_SRCPREF_COA;
-	}
+	else if (sk)
+		flags |= rt6_srcprefs2flags(inet6_sk(sk)->srcprefs);
 
 	return fib6_rule_lookup(net, fl, flags, ip6_pol_route_output);
 }