parisc: Provide default implementation for dma_{alloc, free}_attrs

Most architectures that define CONFIG_HAVE_DMA, have implementations for
both dma_alloc_attrs() and dma_free_attrs().  All achitectures that do
not define CONFIG_HAVE_DMA also have both of these definitions provided by
dma-mapping-broken.h.

Add default implementations for these functions on parisc.

Signed-off-by: Damian Hobson-Garcia <dhobsong@igel.co.jp>
Signed-off-by: Helge Deller <deller@gmx.de>