radio: RTC6226: add support to scan valid lower freq channel

Existing scan logic will start repetitive seek
from lower freq and stops when band limit reached,
with this logic valid lower band is always ignored.
Seek one more time one band limit reached to check
if lower freq channel is valid.

CRs-Fixed: 2683848
Change-Id: I0b2608b544e0402298d1dfdc1bef96ff8ca64123
Signed-off-by: himta ram <hram@codeaurora.org>