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>