Allow physregs to occur in the dag with multiple types. Though I don't...

Allow physregs to occur in the dag with multiple types.  Though I don't likethis, it is a requirement on PPC, which can have an f32 value in r3 at onepoint in a function and a f64 value in r3 at another point.  :(

This fixes compilation of mesa

llvm-svn: 23161