JVM is creating too many GC helper threads on T7/M7 linux/sparc platform

The JVM is creating too many GC helper threads on the T7/M7 platform because hotspot does not correctly set the CPU features for the platform.

The "CPU" line in the /proc/cpuinfo file for a T5 looks like this:

cpu : UltraSparc T5 (Niagara5)

Hotspot interprets the "Niagara" and sets Niagara related features.

The "CPU" line in the /proc/cpuinfo file for a T7/M7 looks like this:

cpu : SPARC-M7

Since the current linux/sparc hotspot code does not recognize "SPARC-M7" it used the default number of GC helper threads that is twice what it should be. The linux/sparc hotspot code should recognize the "SPARC-M7" cpu description and set M family related features.