compat: let architectures define __ARCH_WANT_COMPAT_SYS_GETDENTS64

For architecture dependent compat syscalls in common code an architecture
must define something like __ARCH_WANT_<WHATEVER> if it wants to use the
code.
This however is not true for compat_sys_getdents64 for which architectures
must define __ARCH_OMIT_COMPAT_SYS_GETDENTS64 if they do not want the code.

This leads to the situation where all architectures, except mips, get the
compat code but only x86_64, arm64 and the generic syscall architectures
actually use it.

So invert the logic, so that architectures actively must do something to
get the compat code.

This way a couple of architectures get rid of otherwise dead code.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Git-commit: 0473c9b5f05948df780bbc7b996dd7aefc4ec41d
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>