staging: wilc1000: rename s8RSSI of struct rf_info

This patch renames s8RSSI of struct rf_info to rssi
to avoid CamelCase naming convention.

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