Remove dead code in smbfs makefile.

Cc: Al Viro <viro@www.linux.org.uk>
Cc: Tim Shimmin <xfs-masters@oss.sgi.com>
Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>