net: stmmac: dwxgmac2: Only clear interrupts that are active

In DMA interrupt handler we were clearing all interrupts status, even
the ones that were not active. Fix this and only clear the active
interrupts.

Cc: Joao Pinto <jpinto@synopsys.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Signed-off-by: David S. Miller <davem@davemloft.net>