[llvm] [AArch64][NFC] Avoid relocations in LdStNInstrDesc (PR #202025)

[Alexis Engelke via llvm-commits]

aengelke wrote:

Originally, the idea was that there's padding afterwards that couldn't be filled. But looking at the table more closely, most bits were zero anyway, so I compressed it further to now 16B/entry (previously 40B + the size of two relocations).

https://github.com/llvm/llvm-project/pull/202025