spi: spi-altera-dfl: support n5010 feature revision

The Max10 BMC on the Silicom n5010 PAC is slightly different than the
existing BMCs, so use a dedicated feature revision detect it.

Acked-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Tom Rix <trix@redhat.com>
Signed-off-by: Martin Hundebøll <mhu@silicom.dk>
Signed-off-by: Moritz Fischer <mdf@kernel.org>