um: get rid of sysdep/checksum.h

Move those to sys-.../asm/checksum.h, kill include/asm/checksum.h
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/include/asm/checksum.h

-#ifndef __UM_CHECKSUM_H
-#define __UM_CHECKSUM_H
-
-#include "sysdep/checksum.h"
-
-#endif