RTC6226: keep tuned to valid lower band channel for dwell time

While scan operation at rtc6226 driver when band limit
is reached and then we seek with WRAP_ENABLE one more
time to know if lower freq is valid, we update the
valid lower band frequency to user space without keeping
tuned to lower band frequency for specified dwell time.
This leads to tuned freq mismatch between user space and
kernel driver. Keep tuned to valid lower band channel for
dwell time and also scan the lower band frequency channel
once all the frequencies are scanned in the band range.

CRs-Fixed: 2725895
Change-Id: I8efb580c495baa314ef1a162e19c52eafbc085a9
Signed-off-by: himta ram <hram@codeaurora.org>