msm: wlan: Correct the parsing of db.txt

Current kernel parser for db.txt no more supports antenna gain.
So remove the  entries for antenna gain.

CRs-Fixed: 865863
Change-Id: I22f0d512dd608ea7e09aa8fb1bbf6d7ab6610f87
Signed-off-by: Amar Singhal <asinghal@codeaurora.org>