monitor: remove target-specific code from monitor.c

Move target-specific code out of /monitor.c to /target-*/monitor.c,
this will avoid code cluttering and using random ifdeffery.  The solution
is quite simple, but solves the issue of the separation of target-specific
code from monitor.

Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <1441899541-1856-3-git-send-email-den@openvz.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>