staging: IB/ipath: remove sched.h header

sched.h header in ipath_*.c is now unnecessary, since I have added
sched.h in ipath_kernel.h. So remove it.

Signed-off-by: Geliang Tang <geliangtang@163.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>