radeonsi: don't snoop currently-bound GS shader when compiling ES

radeonsi: don't snoop currently-bound GS shader when compiling ES

Instead, pass the layout of GS inputs in memory to the ES using the shader
key. Only 64 bits are needed to represent the layout in the key.

Mixing and matching different VS and GS shaders should now always work.

Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>