staging: wilc1000: rename u8ssidnum in struct hidden_network

This patch renames u8ssidnum to n_ssids that is a member of struct
hidden_network. There is no need to use u8 prefix to show data type so
just rename it.

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