radv: emit shader descriptor pointers consecutively

radv: emit shader descriptor pointers consecutively

This reduces the number of SET_SH_REG packets which are emitted
for applications that use more than one descriptor set per stage.

We should be able to emit more SET_SH_REG packets consecutively
(like push constants and vertex buffers for the vertex stage),
but this will be improved later.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>