[ELF] Support non-RAX/non-adjacent R_X86_64_GOTPC32_TLSDESC/R_X86_64_TLSDESC_CALL

The current TLSDESC optimization code assumes:
```
leaq x@tlsdesc(%rip), %rax
call *x@tlscall(%rax)       # adjacent
```

From https://gitlab.freedesktop.org/mesa/mesa/-/issues/5665 , it seems that the
two instructions may not be adjacent in GCC 10's output:
```
leaq x@tlsdesc(%rip), %rax
something else
call *x@tlscall(%rax)
```

This patch supports the case. While here, support non-RAX registers for
R_X86_64_GOTPC32_TLSDESC, in case the compiler generates inefficient:

```
leaq x@tlsdesc(%rip), %rcx  # or %rdx, %rbx, %rdi, ...
movq %rcx, %rax
call *x@tlscall(%rax)       # GNU ld/gold error for non-RAX
```

Differential Revision: https://reviews.llvm.org/D114416