[PATCH] prism54/islpci_eth.c: dev_kfree_skb used with interrupts disabled

dev_kfree_skb should not be used with interrupts disabled.  Change to
use dev_kfree_skb_irq instead.

Signed-off-by: Graham Gower <graham.gower@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>