staging: IB/ipath: use TASK_COMM_LEN in ipath_portdata

Use comm[TASK_COMM_LEN] instead of comm[16] in ipath_kernel.h.
And add sched.h header in it.

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