net: Split a __sys_bind helper for io_uring

io_uring holds a reference to the file and maintains a
sockaddr_storage address.  Similarly to what was done to
__sys_connect_file, split an internal helper for __sys_bind in
preparation to supporting an io_uring bind command.

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20240614163047.31581-1-krisman@suse.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>