[InlineSpiller] Only account for real spills in the hoisting logic

Spills of undef values shouldn't impact the placement of the relevant
spills. Drive by review.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304850 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed