mwl8k: Tell firmware to generate CCMP header

Post commit e4eefec7

, the stack is
not generating the CCMP header for us anymore. This broke the CCMP
functionality since firmware was not doing this either. Set a flag
to tell the firmware to generate the CCMP header

Signed-off-by: Nishant Sarmukadam <nishants@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>