staging: wilc1000: wilc_spi_read: pass struct wilc

This patch adds new function parameter struct wilc and use it instead of
global variable wilc_dev, and pass wilc to the functions as well.

Signed-off-by: Glen Lee <glen.lee@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>