monitor: uninclude cpu_ldst

This header is non-needed anymore and wont work in multi-arch where
this service is not provided to core code.

Cc: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>
Message-Id: <4e96622ab5320603829b6f94b8c4e94d573d34fc.1441614289.git.crosthwaite.peter@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>