RFR: JDK-8228775: Shenandoah: Remove useless null-input-verification in Shenandoah/C2 verifier

[Roman Kennke]

Post-LRB it doesn't make a difference whether or not inputs to
intrinsics have non-null-types or not because no barriers are feeding
directly into intrinsics. We can remove the whole check.

In sh/jdk11, nightlies are failing because of that, in jdk14 this is
only a bunch of useless code.

Bug:
https://bugs.openjdk.java.net/browse/JDK-8228775
Webrev:
http://cr.openjdk.java.net/~rkennke/JDK-8228775/webrev.00/

Testing: hotspot_gc_shenandoah

Good?

Roman