[MC,AArch64] Suppress local symbol to STT_SECTION conversion for GOT relocations

Assemblers change certain relocations referencing a local symbol to
reference the section symbol instead. This conversion is disabled for
many conditions (`shouldRelocateWithSymbol`), e.g. TLS symbol, for most
targets (including AArch32, x86, PowerPC, and RISC-V) GOT-generating
relocations.

However, AArch64 encodes the GOT-generating intent in MCValue::RefKind
instead of MCSymbolRef::Kind (see commit
0999cbd0 (2014)), therefore not affected
by the code `case MCSymbolRefExpr::VK_GOT:`. As GNU ld and ld.lld
create GOT entries based on the symbol, ignoring addend, the two ldr
instructions will share the same GOT entry, which is not expected:
```
ldr     x1, [x1, :got_lo12:x]  // converted to .data+0
ldr     x1, [x1, :got_lo12:y]  // converted to .data+4

.data
// .globl x, y  would suppress STT_SECTION conversion
x:
.zero 4
y:
.long 42
```

This patch changes AArch64 to suppress local symbol to S...