[DAGCombine] Use APInt::operator|(uint64_t) instead of creating a temporary APInt...

[DAGCombine] Use APInt::operator|(uint64_t) instead of creating a temporary APInt and calling APInt::Or. NFC

This is more efficient by itself. But this is prep for a future patch that may remove APInt::Or while making operator| support rvalue references similar to add/sub.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296981 91177308-0d34-0410-b5e6-96231b3b80d8