PHYLIB: Kconfig: Fix the dependency on S390

 PHYLIB was first marked as BROKEN on S390, then the enclosing menu marked
as non-S390, then the two dependencies merged with the conversion to
menuconfig.  Reduce to non-S390.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>