ANDROID: net: fix 'const' warnings

ANDROID: net: fix 'const' warnings

See the following build log splats. The sock_i_uid() helper doesn't
quite treat the parameter as 'const' (it acquires a member lock), but
this cast is the same approach taken by other callers in this file, so I
don't feel too bad about the fix.

  CC      net/ipv4/inet_connection_sock.o
  CC      net/ipv6/inet6_connection_sock.o
net/ipv6/inet6_connection_sock.c: In function ‘inet6_csk_route_req’:
net/ipv6/inet6_connection_sock.c:89:2: warning: passing argument 1 of ‘sock_i_uid’ discards ‘const’ qualifier from pointer target type [enabled by default]
In file included from include/linux/tcp.h:22:0,
                 from include/linux/ipv6.h:73,
                 from net/ipv6/inet6_connection_sock.c:18:
include/net/sock.h:1689:8: note: expected ‘struct sock *’ but argument is of type ‘const struct sock *’
net/ipv4/inet_connection_sock.c: In function ‘inet_csk_route_req’:
net/ipv4/inet_connection_sock.c:423:7: warning: passing argument 1 of ‘sock_i_uid’ discards ‘const’ qualifier from pointer target type [enabled by default]
In file included from include/net/inet_sock.h:27:0,
                 from include/net/inet_connection_sock.h:23,
                 from net/ipv4/inet_connection_sock.c:19:
include/net/sock.h:1689:8: note: expected ‘struct sock *’ but argument is of type ‘const struct sock *’
net/ipv4/inet_connection_sock.c: In function ‘inet_csk_route_child_sock’:
net/ipv4/inet_connection_sock.c:460:7: warning: passing argument 1 of ‘sock_i_uid’ discards ‘const’ qualifier from pointer target type [enabled by default]
In file included from include/net/inet_sock.h:27:0,
                 from include/net/inet_connection_sock.h:23,
                 from net/ipv4/inet_connection_sock.c:19:
include/net/sock.h:1689:8: note: expected ‘struct sock *’ but argument is of type ‘const struct sock *’

Change-Id: I5c156fc1a81f90323717bffd93c31d205b85620c
Signed-off-by: Brian Norris <briannorris@google.com>