qemu-system-tricore: segfault when entering "x 0" on the monitor

Starting Qemu with "qemu-system-tricore -nographic -M tricore_testboard -S"
and entering "x 0" at the monitor prompt leads to Segmentation fault.
This happens because tricore_cpu_get_phys_page_debug() is not implemented
yet, this is a temporary workaround to avoid the crash.

Signed-off-by: Eduardo Otubo <otubo@redhat.com>
Tested-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
