staging: wilc1000: fix registration frame size

Fixes the following sparse warnings:

drivers/staging/wilc1000/host_interface.c:2360:30: warning:
 incorrect type in assignment (different base types)
    expected restricted __le32 [addressable] [assigned] [usertype] frame_type
    got restricted __le16 [usertype] <noident>

Fixes: 147ccfd4 ("staging: wilc1000: handle mgmt_frame_register ops from cfg82011 context")
Signed-off-by: Július Milan <jmilan.dev@gmail.com>
Reviewed-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>