[DirectX] Fix i8 alignment in datalayout of lit test

An llc lit test used overaligned i8, apparently originating from the old DXIL data layout.
The new DXIL data layout uses naturally aligned i8.

llc ignores the data layout of a module and instead sets the data layout based
on the target. Change the data layout string in the test to match that target-derived
data layout.

Author: jasilvanus

llvm/test/tools/dxil-dis/opaque-value_as_metadata.ll

@@ -1,5 +1,5 @@
 ; RUN: llc --filetype=obj %s -o - 2>&1 | dxil-dis -o - | FileCheck %s
-target datalayout = "e-m:e-p:32:32-i1:32-i8:32-i16:32-i32:32-i64:64-f16:32-f32:32-f64:64-n8:16:32:64"
+target datalayout = "e-m:e-p:32:32-i1:32-i8:8-i16:16-i32:32-i64:64-f16:16-f32:32-f64:64-n8:16:32:64"
 target triple = "dxil-unknown-shadermodel6.7-library"
 
 %"$Globals" = type { float }