r176991 - Really fix the MIPS test.

Darn. I was thinking of trying this prefix match yesterday but was in a hurry and just opted to mimick some tests that were already there. I was nervous that other unrelated changes could break the test and they did.

Why not just :

// CHECK: attributes [[MIPS16]] = { {{.*}} "mips16" {{.*}} }
// CHECK: attributes [[NOMIPS16]] = { {{.*}} "nomips16" {{.*}} }