headers: remove sched.h from interrupt.h

After m68k's task_thread_info() doesn't refer to current,
it's possible to remove sched.h from interrupt.h and not break m68k!
Many thanks to Heiko Carstens for allowing this.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
diff --git a/drivers/net/wireless/prism54/islpci_dev.c b/drivers/net/wireless/prism54/islpci_dev.c
index e26d7b3..2505be5 100644
--- a/drivers/net/wireless/prism54/islpci_dev.c
+++ b/drivers/net/wireless/prism54/islpci_dev.c
@@ -23,6 +23,7 @@
 #include <linux/netdevice.h>
 #include <linux/ethtool.h>
 #include <linux/pci.h>
+#include <linux/sched.h>
 #include <linux/etherdevice.h>
 #include <linux/delay.h>
 #include <linux/if_arp.h>