tpm: Avoid qerror_report() outside QMP command handlers

qerror_report() is a transitional interface to help with converting
existing monitor commands to QMP.  It should not be used elsewhere.
Replace by error_report().

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>