ntb_perf: Schedule based on time not on performance
When debugging performance problems, if some issue causes the ntb
hardware to be significantly slower than expected, ntb_perf will
hang requiring a reboot because it only schedules once every 4GB.
Instead, schedule based on jiffies so it will not hang the CPU if
the transfer is slow.
Signed-off-by: Logan Gunthorpe <logang@deltatee.com> Acked-by: Dave Jiang <dave.jiang@intel.com> Signed-off-by: Jon Mason <jdmason@kudzu.us>