[PATCH] uml: fix missing subdir in x86_64

make distclean et.al.  are missing arch/um/sys-x86_64/utils; fixed the same
way we have it done for sys-i386 counterpart.

Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>