wiznet: Add missing #include <linux/irq.h>

m68k/allmodconfig:

drivers/net/ethernet/wiznet/w5100.c: In function ‘w5100_hw_probe’:
drivers/net/ethernet/wiznet/w5100.c:680: error: ‘IRQ_TYPE_LEVEL_LOW’ undeclared (first use in this function)
drivers/net/ethernet/wiznet/w5300.c: In function ‘w5300_hw_probe’:
drivers/net/ethernet/wiznet/w5300.c:594: error: ‘IRQ_TYPE_LEVEL_LOW’ undeclared (first use in this function)

Include <linux/irq.h>, which provides the declaration for IRQ_TYPE_LEVEL_LOW.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: David S. Miller <davem@davemloft.net>