consolidate asm/const.h to linux/const.h

Make a global linux/const.h header file instead of having multiple,
per-arch files, and convert current users of asm/const.h to use
linux/const.h.

Built on x86_64 and sparc64.

[akpm@linux-foundation.org: fix include/asm-x86_64/Kbuild]
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/asm-x86_64/pgtable.h b/include/asm-x86_64/pgtable.h
index b210838..4e86aca 100644
--- a/include/asm-x86_64/pgtable.h
+++ b/include/asm-x86_64/pgtable.h
@@ -1,7 +1,7 @@
 #ifndef _X86_64_PGTABLE_H
 #define _X86_64_PGTABLE_H
 
-#include <asm/const.h>
+#include <linux/const.h>
 #ifndef __ASSEMBLY__
 
 /*