FM: Reduce high scan time

Changed logic to find Lower Band Limit from Search Up from current
channel with Wrap enable to tuning to Lower Band Limit + chan space
and Search Down with Wrap disable.

Change-Id: I79a686238d96db5dd5df9436b346b465435ae4f5
Signed-off-by: Prateek Raj Singh <pratsing@codeaurora.org>