RFR(M) 8150353: PPC64LE: Support RTM on linux

[Gustavo Romero]

Hi Martin,

Both little and big endian Linux kernel contain the syscall change, so
I did not include:

#if defined(COMPILER2) && (defined(AIX) || defined(VM_LITTLE_ENDIAN)

in globalDefinitions_ppc.hpp.

Please, could you review the following change?

Bug: https://bugs.openjdk.java.net/browse/JDK-8150353
Webrev (hotspot): http://81.de.7a9f.ip4.static.sl-reverse.com/webrev/

Summary:

* Enable RTM support for Linux on PPC64 (LE and BE).
* Fix C2 compiler buffer size issue.

Thank you.

Regards,
Gustavo