Don't create a MIN/MAX node if the underlying compare has more than one use.

Don't create a MIN/MAX node if the underlying compare has more than one use.

If the compare in a select pattern has another use then it can't be removed, so we'd just
be creating repeated code if we created a min/max node.

Spotted by Matt Arsenault!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239037 91177308-0d34-0410-b5e6-96231b3b80d8