zink: Remove leftover dead code.

Fix defect reported by Coverity Scan.

Structurally dead code (UNREACHABLE)
unreachable: This code cannot be reached: return progress;

Fixes: d550c5780f ("zink: use nir_shader_instructions_pass for draw params pass")
Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9182>

src/gallium/drivers/zink/zink_compiler.c

@@ -248,8 +248,6 @@ lower_basevertex_instr(nir_builder *b, nir_instr *in, void *data)
 static bool
 lower_basevertex(nir_shader *shader)
 {
-   bool progress = false;
-
    if (shader->info.stage != MESA_SHADER_VERTEX)
       return false;
 
@@ -257,8 +255,6 @@ lower_basevertex(nir_shader *shader)
       return false;
 
    return nir_shader_instructions_pass(shader, lower_basevertex_instr, nir_metadata_dominance, NULL);
-
-   return progress;
 }