[10] [ppc] RFR(XS): 8180612: assert failure due to immediate value out of range

[Schmidt, Lutz]

Hi all, 

May I kindly request reviews for this small fix? A voluntary sponsor would be great as well!

Bug:    https://bugs.openjdk.java.net/browse/JDK-8180612
Webrev: http://cr.openjdk.java.net/~lucy/webrevs/8180612.00/

The RTM code generation on ppc relied on RTM-related cmdline parameters to provide “well-behaved” values only. At least one jtreg test breaks this assumption. The fix makes code generation adapt to actual parameter values. 

Thanks,
Lutz