staging: ks7010: refactor ks_wlan_get_mode function

Avoid the use of switch-case block which is not necessary
at all and just use a ternary operator to achieve this.

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