[PATCH] fix missing ifdefs in syscall classes hookup for generic targets

several targets have no ....at() family and m32r calls its only chown variant
chown32(), with __NR_chown being undefined.  creat(2) is also absent in some
targets.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>