[clang] [AArch64][SME] Remove immediate argument restriction for svldr and svstr (PR #68565)

[Sander de Smalen via cfe-commits]

https://github.com/sdesmalen-arm commented:

The changes to the LLVM IR intrinsics are to better utilise the reg+imm form of the instructions, but they aren't required to remove the immediate-argument restriction for svldr/svstr. I think it would be better to split the PR into two PRs:
* One patch that fixes `vnum` (uint64_t -> int64_t) and removes the 'must be immediate argument' restriction.
* Another patch that tries to better use the immediate in the instruction by changing the LLVM IR intrinsic with an extra parameter.

https://github.com/llvm/llvm-project/pull/68565