staging: ks7010: Change mac_address_valid to a bool instead of int.

'mac_address_valid' is only ever assigned 0 or 1, so it makes more sense
to use a bool type for this variable.

Signed-off-by: Quytelda Kahja <quytelda@tamalin.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>