KVM: PPC: Book3S HV: Turn "KVM guest htab" message into a debug message

The average user likely does not know what a "htab" or "LPID" is,
and it's annoying that these messages are quickly filling the dmesg
log when you're doing boot cycle tests, so let's turn it into a debug
message instead.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>