[debuginfo] Fix broken tests from MachineLICM salvaging fix

Previous commit: bd7ff5d9

- Added missing x86 triples
- Added missing asserts

llvm/test/DebugInfo/MIR/X86/mlicm-hoist-post-regalloc.mir

 --- |
-  ; RUN: llc -start-before=phi-node-elimination -stop-after=machinelicm -o - %s  | FileCheck %s
+  ; REQUIRES: asserts
+  ; RUN: llc -start-before=phi-node-elimination -stop-after=machinelicm -debug-only=machinelicm -o - %s  | FileCheck %s
   ; Ensure we execute machinelicm post register allocation.
   ; Line numbers should not be retained when loop invariant instructions are hoisted.
   ;
@@ -7,6 +8,7 @@
   ; CHECK:        MOV64rm $rip, 1, $noreg, target-flags(x86-gotpcrel) @x, $noreg :: (load 8 from got)
   ; CHECK-LABEL:  bb.1.while.body:
   ;
+  target triple = "x86_64-unknown-linux-gnu"
 
   @x = common local_unnamed_addr global i32 0, align 4, !dbg !0
 

llvm/test/DebugInfo/MIR/X86/mlicm-hoist-pre-regalloc.mir

---- |
+--- | 
   ; RUN: llc -run-pass=machinelicm -o - %s | FileCheck %s
   ; Line numbers should not be retained when loop invariant instructions are hoisted.
   ; Doing so causes poor stepping bevavior.
@@ -23,6 +23,7 @@
   ;
   ; ModuleID = 'tx.ll'
   source_filename = "t.c"
+  target triple = "x86_64-unknown-linux-gnu"
 
   @x = common local_unnamed_addr global i32 0, align 4, !dbg !0
 

llvm/test/DebugInfo/MIR/X86/mlicm-sink.mir

@@ -4,6 +4,7 @@
   ; CHECK: %0:gr64 = nuw ADD64ri8 %9, 4, implicit-def dead $eflags
   ; 
   ; When instructions are sunk to prevent register spills, line numbers should not be retained.
+   target triple = "x86_64-unknown-linux-gnu"
 
   %struct.A = type { i32, i32, i32, i32, i32, i32 }