RFR(S): 8211145: [ppc] [s390]: Build fails due to -Werror=switch (introduced with JDK-8211029)

[Schmidt, Lutz]

Dear all,

may I please request reviews for this small patch, fixing some “default case missing” issues in platform code (ppc and s390).

Bug:    https://bugs.openjdk.java.net/browse/JDK-8211145
Webrev: http://cr.openjdk.java.net/~lucy/webrevs/8211145.00/

Thank you,
Lutz