anv/cmd_buffer: Use some pre-existing pipeline temporaries

anv/cmd_buffer: Use some pre-existing pipeline temporaries

There are several places where we'd already saved the pipeline off to a
temporary variable but, due to an artifact of history, weren't actually
using that temporary everywhere.  No functional change.

Tested-by: Józef Kucia <joseph.kucia@gmail.com>
Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Cc: "18.0" <mesa-stable@lists.freedesktop.org>