ir3/lower_pcopy: Fix shr.b illegal copy lowering

The immediate shouldn't be half-reg because the other source isn't.
Fixes an assertion failure with
dEQP-VK.ssbo.phys.layout.random.16bit.scalar.35.

Fixes: 0ffcb19b9d ("ir3: Rewrite register allocation")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13818>

src/freedreno/ir3/ir3_lower_parallelcopy.c

@@ -223,12 +223,12 @@ do_copy(struct ir3_compiler *compiler, struct ir3_instruction *instr,
             cov->cat1.src_type = TYPE_U32;
             ir3_instr_move_before(cov, instr);
          } else {
-            /* shr.b dst, src, h(16) */
+            /* shr.b dst, src, (16) */
             struct ir3_instruction *shr =
                ir3_instr_create(instr->block, OPC_SHR_B, 1, 2);
             ir3_dst_create(shr, dst_num, entry->flags);
             ir3_src_create(shr, src_num, entry->flags & ~IR3_REG_HALF);
-            ir3_src_create(shr, 0, entry->flags | IR3_REG_IMMED)->uim_val = 16;
+            ir3_src_create(shr, 0, IR3_REG_IMMED)->uim_val = 16;
             ir3_instr_move_before(shr, instr);
          }
          return;