powerpc: use <asm-generic/dma-mapping.h>

The powerpc version of dma-mapping.h only contains a version of
get_arch_dma_ops that always return NULL.  Replace it with the
asm-generic version that does the same.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190807150752.17894-1-hch@lst.de

arch/powerpc/include/asm/Kbuild

@@ -4,6 +4,7 @@ generated-y += syscall_table_64.h
 generated-y += syscall_table_c32.h
 generated-y += syscall_table_spu.h
 generic-y += div64.h
+generic-y += dma-mapping.h
 generic-y += export.h
 generic-y += irq_regs.h
 generic-y += local64.h

arch/powerpc/include/asm/dma-mapping.h

-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- * Copyright (C) 2004 IBM
- */
-#ifndef _ASM_DMA_MAPPING_H
-#define _ASM_DMA_MAPPING_H
-
-static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
-{
-	/* We don't handle the NULL dev case for ISA for now. We could
-	 * do it via an out of line call but it is not needed for now. The
-	 * only ISA DMA device we support is the floppy and we have a hack
-	 * in the floppy driver directly to get a device for us.
-	 */
-	return NULL;
-}
-
-#endif	/* _ASM_DMA_MAPPING_H */