qcacmn: Add support to dynamically set dwell time for 2g

Currently there is no support to dynamically set dwell time
for 2g channels.
Add support in existing command SETDWELLTIME to dynamically
configure dwell time for 2g channels.
Along with set, add support to get dwell time for 2g channels
with the existing driver command GETDWELLTIME.

Change-Id: I8a71e39338e7a81690140f50bc3c5ac7b0bd63eb
CRs-Fixed: 2620370
3 files changed