i965/nir: Remove return handling

This was added because we were getting spurrious returns coming out of
SPIR-V.  Now that we're calling lower_returns, we don't need this.

src/mesa/drivers/dri/i965/brw_fs_nir.cpp

@@ -2944,12 +2944,6 @@ fs_visitor::nir_emit_jump(const fs_builder &bld, nir_jump_instr *instr)
       bld.emit(BRW_OPCODE_CONTINUE);
       break;
    case nir_jump_return:
-      /* This has to be the last block in the shader.  We don't handle
-       * early returns.
-       */
-      assert(nir_cf_node_next(&instr->instr.block->cf_node) == NULL &&
-             instr->instr.block->cf_node.parent->type == nir_cf_node_function);
-      break;
    default:
       unreachable("unknown jump");
    }

src/mesa/drivers/dri/i965/brw_vec4_nir.cpp

@@ -1482,13 +1482,6 @@ vec4_visitor::nir_emit_jump(nir_jump_instr *instr)
       break;
 
    case nir_jump_return:
-      /* This has to be the last block in the shader.  We don't handle
-       * early returns.
-       */
-      assert(nir_cf_node_next(&instr->instr.block->cf_node) == NULL &&
-             instr->instr.block->cf_node.parent->type == nir_cf_node_function);
-      break;
-
    default:
       unreachable("unknown jump");
    }