[AArch64][SME] Fix restoring callee-saves from FP with hazard padding

Currently, when hazard-padding is enabled a (fixed-size) hazard slot is
placed in the CS area, just after the frame record. The size of this
slot is part of the "CalleeSaveBaseToFrameRecordOffset". The SVE
epilogue emission code assumed this offset was always zero, and
incorrectly setting the stack pointer, resulting in all SVE registers
being reloaded from incorrect offsets.

```
| prev_lr                           |
| prev_fp                           |
| (a.k.a. "frame record")           |
|-----------------------------------| <- fp(=x29)
|   <hazard padding>                |
|-----------------------------------| <- callee-saved base
|                                   |
| callee-saved fp/simd/SVE regs     |
|                                   |
|-----------------------------------| <- SVE callee-save base
```

i.e. in the above diagram, the code assumed `fp == callee-saved base`.

Author: MacDue

llvm/lib/Target/AArch64/AArch64FrameLowering.cpp

@@ -2539,13 +2539,15 @@ void AArch64FrameLowering::emitEpilogue(MachineFunction &MF,
     // restore the stack pointer from the frame pointer prior to SVE CSR
     // restoration.
     if (AFI->isStackRealigned() || MFI.hasVarSizedObjects()) {
-      if (int64_t CalleeSavedSize = AFI->getSVECalleeSavedStackSize()) {
+      if (int64_t SVECalleeSavedSize = AFI->getSVECalleeSavedStackSize()) {
         // Set SP to start of SVE callee-save area from which they can
         // be reloaded. The code below will deallocate the stack space
         // space by moving FP -> SP.
-        emitFrameOffset(MBB, RestoreBegin, DL, AArch64::SP, AArch64::FP,
-                        StackOffset::getScalable(-CalleeSavedSize), TII,
-                        MachineInstr::FrameDestroy);
+        emitFrameOffset(
+            MBB, RestoreBegin, DL, AArch64::SP, AArch64::FP,
+            StackOffset::get(-AFI->getCalleeSaveBaseToFrameRecordOffset(),
+                             -SVECalleeSavedSize),
+            TII, MachineInstr::FrameDestroy);
       }
     } else {
       if (AFI->getSVECalleeSavedStackSize()) {