cpufreq: interactive: Revert sync on thread migration optimizations

Commit f8b276565ce95bd788af0fc8d060f92632590a40
(cpufreq: Sync on thread migration optimizations) is no longer needed
for targets with synchronous CPUs.

Part of that commit has already been reverted in
a913b3afcaa55356f5f793ae895312c8ae7e1f71
(cpufreq: interactive: Revert timer start modification)

This commit reverts the remaining changes.

Change-Id: I7eadeb7e48cfbef8fec74eb1b0e221eb65482f52
Signed-off-by: Junjie Wu <junjiew@codeaurora.org>

Conflicts:
	drivers/cpufreq/cpufreq_interactive.c