[mlir] Fix LLVM intrinsic convesion generator for overloadable types.

Summary:
If an intrinsic has overloadable types like llvm_anyint_ty or
llvm_anyfloat_ty then to getDeclaration() we need to pass a list
of the types that are "undefined" essentially concretizing them.

This patch add support for deriving such types from the MLIR op
that has been matched.

Reviewers: andydavis1, ftynse, nicolasvasilache, antiagainst

Subscribers: mehdi_amini, rriddle, jpienaar, burmako, shauheen, arpith-jacob, mgester, lucyrfox, liufengdb, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D72974