[WebAssembly] Emit .param, .result, and .local through MC.

This eliminates one of the main remaining uses of EmitRawText.

llvm-svn: 253878
diff --git a/llvm/test/CodeGen/WebAssembly/f64.ll b/llvm/test/CodeGen/WebAssembly/f64.ll
index 44ab1e6..927a571 100644
--- a/llvm/test/CodeGen/WebAssembly/f64.ll
+++ b/llvm/test/CodeGen/WebAssembly/f64.ll
@@ -15,8 +15,7 @@
 declare double @llvm.rint.f64(double)
 
 ; CHECK-LABEL: fadd64:
-; CHECK-NEXT: .param f64{{$}}
-; CHECK-NEXT: .param f64{{$}}
+; CHECK-NEXT: .param f64, f64{{$}}
 ; CHECK-NEXT: .result f64{{$}}
 ; CHECK-NEXT: f64.add $push0, $0, $1{{$}}
 ; CHECK-NEXT: return $pop0{{$}}