cpufreq: interactive: Don't set floor_validate_time during boost

Frequency selection algorithm guarantees its chosen frequency
is not lower than hispeed_freq as long as boost is enabled.

Setting floor_freq and floor_validate_time during boost could block
CPU frequency from going below hispeed_freq even after
boostpulse_duration expires, if min_sample_time is higher than
boostpulse_duration. This conflicts with the intention of commit
de091367
(cpufreq: interactive: specify duration of CPU speed boost pulse)
to allow CPU to ramp down immediately after boost expires. It also
makes boost behavior inconsistent since it depends on min_sample_time.

Avoid setting floor_freq and floor_validate_time when boost starts.

Change-Id: I12852998af46cfbfaf8661eb5e8d5301b6f631e7
Signed-off-by: Junjie Wu <junjiew@codeaurora.org>