MIPS: Don't use dma_cache_sync to implement fd_cacheflush

MIPS: Don't use dma_cache_sync to implement fd_cacheflush

The floppy drivers doesn't otherwise use the DMA API, so indirecting
through it just for cache flushing in MIPS-specific code just call
dma_cache_wback_inv directly.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: iommu@lists.linux-foundation.org
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Michal Simek <monstr@monstr.eu>
Cc: David Howells <dhowells@redhat.com>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: x86@kernel.org
Cc: linux-mips@linux-mips.org
Cc: linux-ia64@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-xtensa@linux-xtensa.org
Cc: linux-sh@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/17183/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>