smb3: add trace point for SMB2_set_eof

In order to debug problems with file size being reported incorrectly
temporarily (in this case xfstest generic/584 intermittent failure)
we need to add trace point for the non-compounded code path where
we set the file size (SMB2_set_eof).  The new trace point is:
   "smb3_set_eof"

Here is sample output from the tracepoint:

            TASK-PID     CPU#  |||||  TIMESTAMP  FUNCTION
              | |         |   |||||     |         |
          xfs_io-75403   [002] ..... 95219.189835: smb3_set_eof: xid=221 sid=0xeef1cbd2 tid=0x27079ee6 fid=0x52edb58c offset=0x100000
 aio-dio-append--75418   [010] ..... 95219.242402: smb3_set_eof: xid=226 sid=0xeef1cbd2 tid=0x27079ee6 fid=0xae89852d offset=0x0

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