net: macb: Properly add DMACFG bit definitions

Add *_SIZE macros for the bits ENDIA_DESC and
ENDIA_PKT

Signed-off-by: Arun Chandran <achandran@mvista.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>