asm-generic: remove ISA_DMA_THRESHOLD in scatterlist.h

This is the first half of the attempt to use asm-generic/scatterlist.h
on every architecture.

There are only two ways to define scatterlist structure. So it's easy
to convert every architecture to use asm-generic/scatterlist.h.

This patch:

The trick for ISA_DMA_THRESHOLD in asm-generic/scatterlist.h doesn't work
for powerpc. This lets architectures defin ISA_DMA_THRESHOLD.

Hopefully, we can remove ISA_DMA_THRESHOLD in the future; we can do better
to decide if the bouncing is necessary or not.

Signed-off-by: FUJITA Tomonori <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Cc: Richard Henderson <[e-mail]>
Cc: Ivan Kokshaysky <[e-mail]>
Cc: Matt Turner <[e-mail]>
Cc: Russell King <[e-mail]>
Cc: Benjamin Herrenschmidt <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/microblaze/include/asm/scatterlist.h

···
+#define ISA_DMA_THRESHOLD	(~0UL)
+
 #include <asm-generic/scatterlist.h>

arch/s390/include/asm/scatterlist.h

···
+#define ISA_DMA_THRESHOLD	(~0UL)
+
 #include <asm-generic/scatterlist.h>

arch/score/include/asm/scatterlist.h

···
 #ifndef _ASM_SCORE_SCATTERLIST_H
 #define _ASM_SCORE_SCATTERLIST_H
 
+#define ISA_DMA_THRESHOLD	(~0UL)
+
 #include <asm-generic/scatterlist.h>
 
 #endif /* _ASM_SCORE_SCATTERLIST_H */

arch/sparc/include/asm/scatterlist.h

···
 
 #define sg_dma_len(sg)     	((sg)->dma_length)
 
+#define ISA_DMA_THRESHOLD	(~0UL)
+
 #include <asm-generic/scatterlist.h>
 
 #endif /* !(_SPARC_SCATTERLIST_H) */

include/asm-generic/scatterlist.h

···
 #endif /* 64 bit */
 #endif /* sg_dma_len */
 
-#ifndef ISA_DMA_THRESHOLD
-#define ISA_DMA_THRESHOLD	(~0UL)
-#endif
-
 #define ARCH_HAS_SG_CHAIN
 
 #endif /* __ASM_GENERIC_SCATTERLIST_H */