While converting compat system call handlers to work on 32-bit
architectures, I found a number of types used in those handlers
that are identical between all architectures.

Let's move all the identical ones into asm-generic/compat.h to avoid
having to add even more identical definitions of those types.

For unknown reasons, mips defines __compat_gid32_t, __compat_uid32_t
and compat_caddr_t as signed, while all others have them unsigned.
This seems to be a mistake, but I'm leaving it alone here. The other
types all differ by size or alignment on at least on architecture.

compat_aio_context_t is currently defined in linux/compat.h but
also needed for compat_sys_io_getevents(), so let's move it into
the same place.

While we still have not decided whether the 32-bit time handling
will always use the compat syscalls, or in which form, I think this
is a useful cleanup that we can merge regardless.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

We have a couple of files that try to include asm/compat.h on
architectures where this is available. Those should generally use the
higher-level linux/compat.h file, but that in turn fails to include
asm/compat.h when CONFIG_COMPAT is disabled, unless we can provide
that header on all architectures.

This adds the asm/compat.h for all remaining architectures to
simplify the dependencies.

Architectures that are getting removed in linux-4.17 are not changed
here, to avoid needless conflicts with the removal patches. Those
architectures are broken by this patch, but we have already shown
that they have no users.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>