staging: wilc1000: fix incorrect allocation size for structure

Currently the allocation for str_vals is for the sizeof the pointer
rather than the size of the structure.  Fix this.

Detected by smatch
"wilc_wlan_cfg_init() error: not allocating enough data 392 vs 8"

Fixes: acceb12a ("staging: wilc1000: refactor code to avoid static variables for config parameters")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>