cifs: add spinlock for the openFileList to cifsInodeInfo

cifs: add spinlock for the openFileList to cifsInodeInfo

We can not depend on the tcon->open_file_lock here since in multiuser mode
we may have the same file/inode open via multiple different tcons.

The current code is race prone and will crash if one user deletes a file
at the same time a different user opens/create the file.

To avoid this we need to have a spinlock attached to the inode and not the tcon.

RHBZ:  1580165

CC: Stable <[email protected]>
Signed-off-by: Ronnie Sahlberg <[email protected]>
Signed-off-by: Steve French <[email protected]>
Reviewed-by: Pavel Shilovsky <[email protected]>