wil6210: option to override A-BFT length in start AP/PCP

Add an option to specify and override the A-BFT length when
starting an AP/PCP. See IEEE P802.11-2016, 10.38.5.
The abft_len must be set before starting AP/PCP. It is only
needed for diagnostics and certification.

Change-Id: Idb7a72b1a3c87c0ca085ca55a9e2507d14eecbdb
Signed-off-by: Lior David <qca_liord@qca.qualcomm.com>
Signed-off-by: Maya Erez <qca_merez@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
Git-commit: c3bfea05a6fdecee03c7cf08f5bfee6aa0645cee
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git


Signed-off-by: Maya Erez <merez@codeaurora.org>