tpm: rename qemu_find_tpm() -> qemu_find_tpm_be()

find_tpm() will be introduced to lookup the TPM device.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>