[9] RFR(S) 8129893: 8129094 fix is incomplete

[Vladimir Kozlov]

http://cr.openjdk.java.net/~kvn/8129893/webrev/
https://bugs.openjdk.java.net/browse/JDK-8129893

Current checks missed EncodeP node.
Move primitive type check from under n->is_Mem() check.
Add second primitive type to guarantee that we don't execute following 
code for non-primitive type node.

Tested with failed CTW test.

thanks,
Vladimir