net: bcmgenet: add UMAC_IRQ_RXDMA_DONE and UMAC_IRQ_TXDMA_DONE

Add #define for UMAC_IRQ_RXDMA_DONE and UMAC_IRQ_TXDMA_DONE in order
to simplify the code that handles Rx and Tx default queue interrupts.

Signed-off-by: Petri Gynther <pgynther@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>