net/rds: Use AF_INET for sin_family field

Elsewhere the sin_family field holds a value with a name of the form
AF_..., so it seems reasonable to do so here as well.  Also the values of
PF_INET and AF_INET are the same.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/

)

// <smpl>
@@
struct sockaddr_in sip;
@@

(
sip.sin_family ==
- PF_INET
+ AF_INET
|
sip.sin_family !=
- PF_INET
+ AF_INET
|
sip.sin_family =
- PF_INET
+ AF_INET
)
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: David S. Miller <davem@davemloft.net>