net: ethernet: mediatek: Explicitly include linux/interrupt.h

The mediatek ethernet driver uses interrupts but does not explicitly
include linux/interrupt.h, relying on implicit includes.  Fix this so we
don't get build breaks as happened for ARM in next-20170720.

Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>