Merge branch 'net-stmmac-dwmac4-auto-discover-uc-filter-size'

Maxime Chevallier says:

====================
net: stmmac: dwmac4: Auto-discover UC filter size

Following my attempts to get clean ethtool selftests runs on stmmac [1],
several issues were found with the unicast filtering.

[1]: https://lore.kernel.org/netdev/20260827134004.45ffb57e@kernel.org/

This lead to the discovery that on dwmac4 platforms, the unicast filter
size is always falling back to the default value of 1 entry. On older
variants, the size comes from devicetree.

With a single-entry filter, we directly fallback to unicast promisc as
soon as any entry is added in the dev->uc list.

dwmac4 exposes through the HW_Features0 register the actual size of the
unicast filter, which is made of 3 banks (details in patch 2). Let's use
this feature to grab the filter size.

Results on actual hardware :

 - imx8mp   : goes from 1 entry to 64
 - stm32mp1 : goes from 1 entry to 4
 - jh7110   : goes from 1 entry to 9
 - yt6801   : still 1 single entry, on extra implemented in HW
====================

Link: https://patch.msgid.link/20260831070121.349778-1-maxime.chevallier@bootlin.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>