[PATCH] asm/generic: fix bug - kernel fails to build when enable some common audit...

If you enable some common audit code, the kernel fails to build.

In file included from lib/audit.c:17:
include/asm-generic/audit_write.h:3: error: '__NR_swapon' undeclared here (not in a function)
make[1]: *** [lib/audit.o] Error 1
make: *** [lib] Error 2

So do not use __NR_swapon if it isnt defined for a port.

Signed-off-by: Mike Frysinger <vapier.adi@gmail.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>