RTC6226: append the valid channel in scan list

During scan operation some channel are getting scanned
with rssi value less then the rssi threshold value.
Append the channel in scan list if it found with rssi
greater or equal to rssi threshold value.
Tune back to the original tuned frequency when scan
is cancelled in between.

CRs-Fixed: 2734678
Change-Id: Ib431ce70e9c32b2ddf3f991b41abc0c23c74e820
Signed-off-by: himta ram <hram@codeaurora.org>