tcg-target.h does not use any QEMU-specific symbols, save for tci's usage
of CPUArchState.  Pull that up to tcg/tcg.h.

This will make it possible to include tcg-target.h in cpu-defs.h.

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