revert r314698 - [InstCombine] remove one-use restriction for icmp (shr exact...

revert r314698 - [InstCombine] remove one-use restriction for icmp (shr exact X, C1), C2 --> icmp X, (C2<<C1)

There is a bot failure that appears to be related to this change:
http://lab.llvm.org:8011/builders/clang-cmake-armv7-a15-selfhost-neon/builds/2117

...so reverting to confirm that and attempting to keep the bot green while investigating.

llvm-svn: 314984