arch: mostly remove <asm/segment.h>

A few architectures use <asm/segment.h> internally, but nothing in
common code does. Remove all the empty or almost empty versions of it,
including the asm-generic one.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/ia64/include/asm/segment.h

@@ -1,6 +0,0 @@
-#ifndef _ASM_IA64_SEGMENT_H
-#define _ASM_IA64_SEGMENT_H
-
-/* Only here because we have some old header files that expect it.. */
-
-#endif /* _ASM_IA64_SEGMENT_H */