add a test for the ud2a alias.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@117803 91177308-0d34-0410-b5e6-96231b3b80d8

test/MC/X86/x86-32.s

@@ -783,6 +783,10 @@ pshufw $90, %mm4, %mm0
 // CHECK:  encoding: [0xdb,0xe2]
         	fnclex
 
+// CHECK: ud2
+// CHECK:  encoding: [0x0f,0x0b]
+        	ud2
+
 // CHECK: ud2
 // CHECK:  encoding: [0x0f,0x0b]
         	ud2a