i2400m: Generic probe/disconnect, reset and message passing

Implements the generic probe and disconnect functions that will be
called by the USB and SDIO driver's probe/disconnect functions.

Implements the backends for the WiMAX stack's basic operations:
message passing, rfkill control and reset.

Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>