staging: ks7010: remove not used function signature ks_wlan_read_config_file

This commit removes definition of function ks_wlan_read_config_file
which is not being used at all.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>