[inline asm] Return an undef SDValue of the expected value type, rather than
report a fatal error.  This allows us to continue processing the translation
unit.  Test case to come on the clang side because we need an inline asm
diagnostics handler in place.
rdar://13446483

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180873 91177308-0d34-0410-b5e6-96231b3b80d8