smb3: add dynamic trace points for tree disconnect

Needed this for debugging a failing xfstest.
Also change camel case for "treeName" to "tree_name" in tcon struct.

Example trace output (from "trace-cmd record -e smb3_tdis*"):
          umount-9718    [006] .....  5909.780244: smb3_tdis_enter: xid=206 sid=0xcf38894e tid=0x3d0b8cf8 path=\\localhost\test
          umount-9718    [007] .....  5909.780878: smb3_tdis_done: xid=206 sid=0xcf38894e tid=0x3d0b8cf8

Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>