We are using the hlsl_ir_var.is_uniform flag to indicate when an object
is a uniform copy created from a variable with the HLSL_STORAGE_UNIFORM
modifier.
We should be checking for this instead of the HLSL_STORAGE_UNIFORM flag
which is also set to 1 for the original variables, and there should be
no reason to use this flag instead of "is_uniform" after the uniform
copies and combined/separated samplers are created.
This struct is required for handling both whole-variable resources for
SM < 5 and single-component resources for SM 5 in the same way, when
writting the RDEF block and resource declarations within the shader.
After lowering the derefs path to a single offset node, there was no way
of knowing the type of the referenced part of the variable. This little
modification allows to avoid having to pass the data type everywhere and
it is required for supporting instructions that reference objects
components within struct types.
Since deref->data_type allows us to retrieve the type of the deref,
deref->offset_regset is no longer necessary.
