cifs: fix locking and list handling code in cifs_open and its helper

The patch to remove cifs_init_private introduced a locking imbalance. It
didn't remove the leftover list addition code and the unlocking in that
function. cifs_new_fileinfo does the list addition now, so there should
be no need to do it outside of that function.

pCifsInode will never be NULL, so we don't need to check for that. This
patch also gets rid of the ugly locking and unlocking across function
calls.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Acked-by: Steve French <sfrench@us.ibm.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>