[llvm] [AMDGPU] In instruction selector, allow copy from physical reg to s1 (PR #96157)

[Jun Wang via llvm-commits]

jwanggit86 wrote:

> You should not have to query whether a register belongs to a register class, only query what that register's class is.

For the problem we are dealing with here, ie. copy from a phys reg to a VCC reg, if you don't query the membership of the phys reg, how do you allow `%0:vcc(s1) = COPY $sgpr0` and disallow `%0:vcc(s1) = COPY $sgpr0_sgpr1`, or vice versa?

https://github.com/llvm/llvm-project/pull/96157