staging: wilc1000: potential corruption in wilc_parse_join_bss_param()

The "rates_len" value needs to be capped so that the memcpy() doesn't
copy beyond the end of the array.

Fixes: c5c77ba1 ("staging: wilc1000: Add SDIO/SPI 802.11 driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Adham Abozaeid <adham.abozaeid@microchip.com>
Link: https://lore.kernel.org/r/20191017091832.GB31278@mwanda


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>