mwl8k: update MODULE_FIRMWARE tags

Add MODULE_FIRMWARE tags for the mwl8k firmware images that don't
have them yet, and move them to where the firmware image names are
declared.

Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>