[GlobalISel][InlineAsm] Add register class ID to the flags of register input operands

Summary: We do this already for output operands, but missed it for (non-tied) input operands.

Reviewers: arsenm, Petar.Avramovic

Reviewed By: arsenm

Subscribers: jvesely, wdng, nhaehnle, rovka, hiraditya, llvm-commits, kerbowa

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D83763