staging: wilc1000: Rename network_info member str_rssi to rssi_history

Change name of str_rssi to rssi_history within the network_info
struct for clarity.

Signed-off-by: Tahia Khan <tahia.khan@gmail.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>