staging: wilc1000: use int instead of int8_t

This patch replaces int8_t with int.
The int8_t should be int. It's used as an index into an array
or -1 for not found.

Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Chaehyun Lim <chaehyun.lim@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>