Print uniform buffer registers as cb#[index].

Print uniform buffer registers as cb#[index].

This matches Shader Model 4+ assembly syntax and helps debug shader
compilation issues.

Change-Id: Iff2a2991794e13476b99e11d6ac07fdf5d37570b
Reviewed-on: https://swiftshader-review.googlesource.com/13928
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>