Add some defines for the mem_info bits, simplify
trace_mem_build_info, and also simplify trace_mem_get_info
by making it a wrapper around trace_mem_build_info.

This paves the way for increasing size_shift by one bit.

Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-id: 1527028012-21888-3-git-send-email-cota@braap.org
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>