Request for reviews (XS): 6787050: assert(n->in(0) == 0L, "no control") with UseCompressedOops on sparcv9

[Vladimir Kozlov]

http://webrev.invokedynamic.info/kvn/6787050/index.html

Fixed 6787050: assert(n->in(0) == 0L,"no control") with UseCompressedOops on sparcv9

Problem:
Regression introduced by the fix for 6782820.
DecodeN could be pinned (has control edge) on platforms (Sparc)
where it can't be fold into the address expression.

Solution:
Relax the assert for such platforms.

Reviewed by:
Fix verified (y/n): y

Other testing:
JPRT