cpufreq: schedutil: Move worker threads back to Real Time

As there are no other DEADLINE class tasks in system, move schedutil
worker threads back to Real Time (SCHED_FIFO) just like previous Kernels.

Change-Id: I1a31bac548493d3c8a22b69b3652c09b1bab4dcd
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>