[PatternMatch] Remove 64-bit or less restriction from m_SpecificInt

Not sure why this restriction existed, but it seems like we should support any size Constant here.

The particular pattern in the tests is not the only use of this matcher in the tree. There's one in CodeGenPrepare and one in InstSimplify as well.

Differential Revision: https://reviews.llvm.org/D34666

llvm-svn: 306417