staging: wilc1000: use int type for counter variable

counter is used as for-loop control variable and indicating index of
struct wid array so that it is better to use int type.
There is no need to set to 0 when it is declared at the top of this
function. It is initialized as 0 in for-loop statement.

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