8248337: sparc related code clean up after solaris removal

[Yumin Qi]

HI,

   Please review for

   bug: https://bugs.openjdk.java.net/browse/JDK-8248337

   webrev:http://cr.openjdk.java.net/~minqi/2020/8248337/webrev-01/


   Summary: After Solaris supported files removed from repo, there are some remnants which needs cleaning up. Some comments are not correct, and some refer to wrong files. There is a flag seems only useful for Sparc: UseRDPCForConstantTableBase, which got removed in this patch . Also in postaloc.cpp, the delay slot seems is only for sparc too, but I am not sure about that. Most of the patch are in comment section.


   Tests passed tier1-4


   Thanks

   Yumin