Add support for scalarizing ctlz_zero_undef

Fix the missing case in ScalarizeVectorResult() that was exposed with
libclcore.bc in Android.

Differential Revision: http://reviews.llvm.org/D4645

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214266 91177308-0d34-0410-b5e6-96231b3b80d8

(cherry picked from commit 63045274)

Change-Id: I38fc81e0ceefd2cfdd65d7619a62124dc4ceac6f