Peter Crosthwaite hasn't had the bandwidth to do code review or
other QEMU work for some time now -- remove his email address
from MAINTAINERS file entries so we don't bombard him with
patch emails.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20190207181422.4907-1-peter.maydell@linaro.org