[JITLink][AArch64] Rename PointerToGOT and fix typo.

PointerToGOT lowering was accidentally changed from Delta32 to Delta64 in
db372258. This patch moves it back to Delta32 and renames the generic
aarch64 edge to Delta32ToGOT to avoid the ambiguity.

No test case yet -- I haven't figured out how to write a succinct test case
(this typically appears in CIEs in eh-frames).