wil6210: add oob_mode module parameter

Add module parameter oob_mode. Takes effect the next time
the interface is brought up and FW is loaded. Puts the FW
in special "out of the box" (OOB) mode which is used for
diagnostics and certification.

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>