RFR: 8292780: misc tests failed "assert(false) failed: graph should be schedulable"

[Roland Westrelin]

PhaseMacroExpand::generate_partial_inlining_block() adds
LoadVectorMasked nodes to the IR graph and then
LoadNode::split_through_phi() tries to split one of them through phi
but because that method ignores the mask input to that LoadNode (it
only knows about control, memory and address inputs) the resulting
graph is broken. Fix I propose is to skip
LoadNode::split_through_phi() for those LoadVector nodes that have
extra inputs.

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Commit messages:
 - fix & test

Changes: https://git.openjdk.org/jdk/pull/10410/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10410&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8292780
  Stats: 52 lines in 2 files changed: 51 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/10410.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10410/head:pull/10410

PR: https://git.openjdk.org/jdk/pull/10410