Revert "builtins: Add ARM Thumb1 implementation for uidiv and uidivmod"

This reverts commit r288710.

r288710 breaks building the builtin libraries on Darwin for armv7em.

Build logs may still be avaialable here:
http://lab.llvm.org:8080/green/job/clang-stage2-configure-Rlto_build/12035/console

llvm-svn: 288773