udp: fix two sparse errors

commit ba418fa3 ("soreuseport: UDP/IPv4 implementation")
added following sparse errors :

net/ipv4/udp.c:433:60: warning: cast from restricted __be16
net/ipv4/udp.c:433:60: warning: incorrect type in argument 1 (different base types)
net/ipv4/udp.c:433:60:    expected unsigned short [unsigned] [usertype] val
net/ipv4/udp.c:433:60:    got restricted __be16 [usertype] sport
net/ipv4/udp.c:433:60: warning: cast from restricted __be16
net/ipv4/udp.c:433:60: warning: cast from restricted __be16
net/ipv4/udp.c:514:60: warning: cast from restricted __be16
net/ipv4/udp.c:514:60: warning: incorrect type in argument 1 (different base types)
net/ipv4/udp.c:514:60:    expected unsigned short [unsigned] [usertype] val
net/ipv4/udp.c:514:60:    got restricted __be16 [usertype] sport
net/ipv4/udp.c:514:60: warning: cast from restricted __be16
net/ipv4/udp.c:514:60: warning: cast from restricted __be16

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>