asm-generic: remove ARCH_HAS_SG_CHAIN in scatterlist.h

There are more architectures that don't support ARCH_HAS_SG_CHAIN than
those that support it.  This removes removes ARCH_HAS_SG_CHAIN in
asm-generic/scatterlist.h and lets arhictectures to define it.

It's clearer than defining ARCH_HAS_SG_CHAIN asm-generic/scatterlist.h and
undefing it in arhictectures that don't support it.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/alpha/include/asm/scatterlist.h

@@ -1,10 +1,8 @@
 #ifndef _ALPHA_SCATTERLIST_H
 #define _ALPHA_SCATTERLIST_H
 
-#define ISA_DMA_THRESHOLD (~0UL)
-
 #include <asm-generic/scatterlist.h>
 
-#undef ARCH_HAS_SG_CHAIN
+#define ISA_DMA_THRESHOLD (~0UL)
 
 #endif /* !(_ALPHA_SCATTERLIST_H) */

arch/arm/include/asm/scatterlist.h

@@ -3,9 +3,6 @@
 
 #include <asm/memory.h>
 #include <asm/types.h>
-
 #include <asm-generic/scatterlist.h>
 
-#undef ARCH_HAS_SG_CHAIN
-
 #endif /* _ASMARM_SCATTERLIST_H */

arch/ia64/include/asm/scatterlist.h

@@ -1,6 +1,7 @@
 #ifndef _ASM_IA64_SCATTERLIST_H
 #define _ASM_IA64_SCATTERLIST_H
 
+#include <asm-generic/scatterlist.h>
 /*
  * It used to be that ISA_DMA_THRESHOLD had something to do with the
  * DMA-limits of ISA-devices.  Nowadays, its only remaining use (apart
@@ -10,7 +11,6 @@
  * that's 4GB - 1.
  */
 #define ISA_DMA_THRESHOLD	0xffffffff
-
-#include <asm-generic/scatterlist.h>
+#define ARCH_HAS_SG_CHAIN
 
 #endif /* _ASM_IA64_SCATTERLIST_H */

arch/microblaze/include/asm/scatterlist.h

@@ -1,3 +1,3 @@
-#define ISA_DMA_THRESHOLD	(~0UL)
-
 #include <asm-generic/scatterlist.h>
+
+#define ISA_DMA_THRESHOLD	(~0UL)

arch/powerpc/include/asm/scatterlist.h

@@ -15,5 +15,6 @@
 #ifdef __powerpc64__
 #define ISA_DMA_THRESHOLD	(~0UL)
 #endif
+#define ARCH_HAS_SG_CHAIN
 
 #endif /* _ASM_POWERPC_SCATTERLIST_H */

arch/sparc/include/asm/scatterlist.h

@@ -1,8 +1,9 @@
 #ifndef _SPARC_SCATTERLIST_H
 #define _SPARC_SCATTERLIST_H
 
-#define ISA_DMA_THRESHOLD	(~0UL)
-
 #include <asm-generic/scatterlist.h>
 
+#define ISA_DMA_THRESHOLD	(~0UL)
+#define ARCH_HAS_SG_CHAIN
+
 #endif /* !(_SPARC_SCATTERLIST_H) */

arch/x86/include/asm/scatterlist.h

@@ -1,8 +1,9 @@
 #ifndef _ASM_X86_SCATTERLIST_H
 #define _ASM_X86_SCATTERLIST_H
 
-#define ISA_DMA_THRESHOLD (0x00ffffff)
-
 #include <asm-generic/scatterlist.h>
 
+#define ISA_DMA_THRESHOLD (0x00ffffff)
+#define ARCH_HAS_SG_CHAIN
+
 #endif /* _ASM_X86_SCATTERLIST_H */

include/asm-generic/scatterlist.h

@@ -31,6 +31,4 @@ struct scatterlist {
 #define sg_dma_len(sg)		((sg)->length)
 #endif
 
-#define ARCH_HAS_SG_CHAIN
-
 #endif /* __ASM_GENERIC_SCATTERLIST_H */