staging: wilc1000: replace u32 with int

The data type of variable i changes u32 to int.
It is used as array index to print debug message so that it is better to
use data type of int.

Signed-off-by: Chaehyun Lim <chaehyun.lim@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>