powerpc/pseries/vio: Don't return ENODEV if node or compatible missing

We noticed the following nuisance messages during boot process:

  vio vio: uevent: failed to send synthetic uevent
  vio 4000: uevent: failed to send synthetic uevent
  vio 4001: uevent: failed to send synthetic uevent
  vio 4002: uevent: failedto send synthetic uevent
  vio 4004: uevent: failed to send synthetic uevent

It's caused by either vio_register_device_node() failing to set
dev->of_node or the node is missing a "compatible" property. To match
the definition of modalias in modalias_show(), remove the return of
ENODEV in such cases. The failure messages is also suppressed with this
change.

Signed-off-by: Lidong Zhong <lidong.zhong@suse.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240411020450.12725-1-lidong.zhong@suse.com