net: mvpp2: Defer probe if MAC address source is not yet ready

NVMEM layouts are no longer registered early, and thus may not yet be
available when Ethernet drivers (or any other consumer) probe, leading
to possible probe deferrals errors. Forward the error code if this
happens. All other errors being discarded, the driver will eventually
use a random MAC address if no other source was considered valid (no
functional change on this regard).

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Marcin Wojtas <mw@semihalf.com>
Link: https://lore.kernel.org/r/20230307192927.512757-1-miquel.raynal@bootlin.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>