linux-user: Tell guest about big host page sizes

linux-user: Tell guest about big host page sizes

We tell the guest its page size via AUX vectors. The guest process then uses
this page size as information on which boundaries it can mmap() things.

However, if the host has a bigger page size granularity than the guest, it can
not fulfill these mmap() requests - which falls apart when MAP_FIXED is passed
to mmap.

So in that case, let the guest know that we're running on a bigger page size
granularity than the target would require.

This fixes running qemu-ppc (TARGET_PAGE_SIZE=4k) on a 64k page size ppc64 host
for me.

Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Richard Henderson <rth@twiddle.net>