staging: wilc1000: handle_cfg_param: remove wrapper struct cfg_param_attr

This struct just wrap struct cfg_param_val. There is no other member
except struct cfg_param_val.
This patch remove struct cfg_param_attr, then struct cfg_param_val is
renamed to struct cfg_param_attr.

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