smb3: fix reset of bytes read and written stats

[ Upstream commit c281bc0c7412308c7ec0888904f7c99353da4796 ]

echo 0 > /proc/fs/cifs/Stats is supposed to reset the stats
but there were four (see example below) that were not reset
(bytes read and witten, total vfs ops and max ops
at one time).

...
0 session 0 share reconnects
Total vfs operations: 100 maximum at one time: 2

1) \\localhost\test
SMBs: 0
Bytes read: 502092  Bytes written: 31457286
TreeConnects: 0 total 0 failed
TreeDisconnects: 0 total 0 failed
...

This patch fixes cifs_stats_proc_write to properly reset
those four.

Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>