mISDN: switch to sock_recvmsg()

here we do need to reinitialize ->msg_iter on each call - the
data in buffer is overwritten every time, not appended to.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2017-09-20 20:11:00 -04:00
commit 956a27ecfa