net: wireless: bcmdhd: Add custom scan policy.

net: wireless: bcmdhd: Add custom scan policy.

Add sysfs node to allow wifi scan policies to be selected / added / removed.

Each wifi scan policy consists of:
- policy name
- one or more scan rules

Each wifi scan rule consists of:
- wait time before starting this scan rule
- scan parameters
  -- home channel away time
  -- number of probes per channel scan
  -- active, passive scan time
  -- home channel dwell time (between channel scans on non-home channel)
  -- channel list to scan

Bug 1573165

Change-Id: I59c0fb563e5ec5677b76e05ea432214e405a51e4
Signed-off-by: Michael Hsu <mhsu@nvidia.com>
Reviewed-on: http://git-master/r/741981
(cherry picked from commit 243a5dba219b94d77e63db925e1746e8f9152d3d)
Reviewed-on: http://git-master/r/755270
Reviewed-by: Ashutosh Jha <ajha@nvidia.com>
Tested-by: Ashutosh Jha <ajha@nvidia.com>