target/hppa: Include "qemu/log.h" to use qemu_log()

Since his inception in 61766fe9, this file uses the qemu_log()
API from "qemu/log.h".  Include it to allow further includes
cleanup.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20180528232719.4721-9-f4bug@amsat.org>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>