[llvm] [clang] ms inline asm: Fix {call,jmp} fptr (PR #73207)

[Fangrui Song via cfe-commits]

MaskRay wrote:

I should confess that I don't understand the mechanism well. I've tried hard to write a good description  but I cannot improve the comments in `CreateMemForMSInlineAsm`.

https://github.com/llvm/llvm-project/pull/73207