hw/xen/xen-mapcache.c: convert DPRINTF to tracepoints

hw/xen/xen-mapcache.c: convert DPRINTF to tracepoints

Tracing DPRINTFs to stderr might not be desired. A developer that relies
on tracepoints should be able to opt-in to each tracepoint and rely on
QEMU's log redirection, instead of stderr by default.

This commit converts DPRINTFs in this file that are used for tracing
into tracepoints.

Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 2fbe1fbc59078e384761c932e97cfa4276a53d75.1706544115.git.manos.pitsidianakis@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>