RFR(XS) 8050165: linux-sparcv9: NMT detail causes assert((intptr_t*)younger_sp[FP->sp_offset_in_saved_window()] == (intptr_t*)((intptr_t)sp - STACK_BIAS)) failed: younger_sp must be valid

[Zhengyu Gu]

Please review this small fix to enable NMT stack walking, also removed 
debugging print. This fix is for 7u80.

Bug: https://bugs.openjdk.java.net/browse/JDK-8050165
Webrev: http://cr.openjdk.java.net/~zgu/8050165/webrev.00/ 
<http://cr.openjdk.java.net/%7Ezgu/8050165/webrev.00/>

Thanks,

-Zhengyu