cifs: append path to open_enter trace event

We do not dump the file path for smb3_open_enter ftrace
calls, which is a severe handicap while debugging
using ftrace evens. This change adds that info.

Unfortunately, we're not updating the path in open params
in many places; which I had to do as a part of this change.
SMB2_open gets path in utf16 format, but it's easier of
path is supplied as char pointer in oparms.

Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Reviewed-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Cc: stable@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>