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

[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.

llvm-svn: 296981