net: stmmac: dwmac4: extend timeout for VLAN Tag register busy bit check

net: stmmac: dwmac4: extend timeout for VLAN Tag register busy bit check

Increase the timeout for checking the busy bit of the VLAN Tag register
from 10µs to 500ms. This change is necessary to accommodate scenarios
where Energy Efficient Ethernet (EEE) is enabled.

Overnight testing revealed that when EEE is active, the busy bit can
remain set for up to approximately 300ms. The new 500ms timeout provides
a safety margin.

Fixes: ed64639bc1e0 ("net: stmmac: Add support for VLAN Rx filtering")
Reviewed-by: Andrew Lunn <[email protected]>
Signed-off-by: Shenwei Wang <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>