[X86] Asm modifier %a: add (%rip) for 64-bit static relocation model
In GCC,
```
static int a;
int foo() {
asm("# %a0" : : "i"(&a));
}
```
lowers to `# a(%rip)` regardless of the PIC mode. This PR follow suits
for ELF -fno-pic, matching ELF -fpic (asm-modifier-pic.ll) and Mach-O
(which defaults to PIC).
Close https://github.com/llvm/llvm-project/issues/139001
Pull Request: https://github.com/llvm/llvm-project/pull/139040