The interrupt status register in both dwmac1000 and dwmac4 ignores
interrupt enable (for dwmac4) / interrupt mask (for dwmac1000).
Therefore, if we want to check only the bits that can actually trigger
an irq, we have to filter the interrupt status register manually.

Commit 0a764db1 ("stmmac: Discard masked flags in interrupt status
register") fixed this for dwmac1000. Fix the same issue for dwmac4.

Just like commit 0a764db1 ("stmmac: Discard masked flags in
interrupt status register"), this makes sure that we do not get
spurious link up/link down prints.
Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>