Tidy logging code not using UNIMPLEMENTED.

Change-Id: I7a79c1671a6ff8b2040887133b3e0925ef9a3cfe
diff --git a/compiler/utils/arm/assembler_arm.cc b/compiler/utils/arm/assembler_arm.cc
index b430c7e..db42b46 100644
--- a/compiler/utils/arm/assembler_arm.cc
+++ b/compiler/utils/arm/assembler_arm.cc
@@ -324,7 +324,7 @@
       return IsAbsoluteUint(10, offset);  // VFP addressing mode.
     default:
       LOG(FATAL) << "UNREACHABLE";
-      return false;
+      UNREACHABLE();
   }
 }
 
@@ -342,7 +342,7 @@
       return IsAbsoluteUint(10, offset);  // VFP addressing mode.
     default:
       LOG(FATAL) << "UNREACHABLE";
-      return false;
+      UNREACHABLE();
   }
 }
 
@@ -359,9 +359,9 @@
       return IsAbsoluteUint(10, offset);  // VFP addressing mode.
     case kLoadWordPair:
       return IsAbsoluteUint(10, offset);
-  default:
+    default:
       LOG(FATAL) << "UNREACHABLE";
-      return false;
+      UNREACHABLE();
   }
 }
 
@@ -377,9 +377,9 @@
       return IsAbsoluteUint(10, offset);  // VFP addressing mode.
     case kStoreWordPair:
       return IsAbsoluteUint(10, offset);
-  default:
+    default:
       LOG(FATAL) << "UNREACHABLE";
-      return false;
+      UNREACHABLE();
   }
 }