RFR(M): 8248191: PPC: Implement Load/Store Vector with lxvl/stxvl in Power10

[joserz at linux.ibm.com]

This patch introduces two instructions lxvl/stvxl and replaces the current lxvd2x/stxvd2x to load and store vectors. Like lxvd2x/stxvd2x, lxvl/stxvl can access unaligned effective addresses with the advantage of *not* requiring xxswapd after lxvd2x (or before stxvd2x) to correct the lanes in little-endian mode.

Webrev: https://cr.openjdk.java.net/~mhorie/8248191/webrev.00/
Bug: https://bugs.openjdk.java.net/browse/JDK-8248191

Thanks for your review!

Jose R. Ziviani