Fix wrong behavior of cpu_memory_rw_debug() function in SMM

Fix wrong behavior of cpu_memory_rw_debug() function in SMM

There is a problem, that you don't have access to the data using cpu_memory_rw_debug() function when in SMM. You can't remotely debug SMM mode program because of that for example.
Likely attrs version of get_phys_page_debug should be used to get correct asidx at the end to handle access properly.
Here the patch to fix it.

Signed-off-by: Dmitry Poletaev <poletaev@ispras.ru>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>