staging: wilc1000: rename result in handle_set_channel

This patch renames result to ret that is used to get return value from
wilc_send_config_pkt.
Some handle_*() function are used as result, others are used as ret.
It will start to rename as ret in all handle_*() function to sync up
with this variable name.

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