wil6210: Tx mgmt frame from debugfs

Provide 2 files on the debugfs:
- "rxon": write channel (1..4) to open Rx on it, 0 to rxoff
- "tx_mgmt": write binary frame, starting from MAC header

one need to care about turning receiver on/off before/after tx_mgmt

Correct sequence is:
 echo $channel > rxon
 cat mfmt_frame > tx_mgmt
 echo 0 > rxon

Change-Id: Ib89a8ea70f8dd722e059f382a6b5a6dc67016ea3
Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Git-commit: 0b39aaf2f2035b1c42b805a786a8b42f7501b82f
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-testing.git


[hkadmany@codeaurora.org: trivial backport to kernel 3.10]
Signed-off-by: Hamad Kadmany <hkadmany@codeaurora.org>