[AArch64] [test] Make unwind info tests actually use the right instructions

This makes them match the expected decoding of the unwind info
opcodes, avoiding mismatch indications from "dumpbin -unwindinfo".

This is a follow up to 4580350;
these cases were missed in that commit.

Author: mstorsjo

llvm/test/MC/AArch64/seh-large-func.s

@@ -192,7 +192,7 @@ b:
 	.seh_save_fplr_x 256
 	stp	x19, x20, [sp, #240]
 	.seh_save_regp x19, 240
-	mov	x29, fp
+	mov	x29, sp
 	.seh_set_fp
 	.seh_endprologue
         .rept 600000

llvm/test/MC/AArch64/seh-optimize.s

@@ -87,7 +87,7 @@ func:
     nop
 
     .seh_startepilogue
-    ldp x27, x28, [sp, #32]
+    ldp x23, x24, [sp, #32]
     .seh_save_regp x23, 32
     ldp x23, x24, [sp, #16]
     .seh_save_regp x23, 16

llvm/test/MC/AArch64/seh-packed-unwind.s

@@ -1078,7 +1078,7 @@ nonpacked9:
     .seh_startepilogue
     mov sp,  x29
     .seh_set_fp
-    ldp x29, lr,  [sp], #32
+    ldp x29, lr,  [sp], #16
     .seh_save_fplr_x 16
     add sp, sp, #32
     .seh_stackalloc 32