staging: wilc1000: clarify the argument type

This patch replaces the void pointer type in the host interface
functions which process the message from host thread by the real data
type, tstrWILC_WFIDrv because the void pointer type as the arguments
is not clear and concise. In addition, typecasting to the void pointer
type is removed becasue it is not necessary.

Signed-off-by: Johnny Kim <johnny.kim@atmel.com>
Signed-off-by: Tony Cho <tony.cho@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>