Blackfin arch: Remove useless head file

Signed-off-by: NGraf Yang <graf.yang@analog.com>
Signed-off-by: NBryan Wu <cooloney@kernel.org>

arch/blackfin/include/asm/cpumask.h

-#ifndef _ASM_BLACKFIN_CPUMASK_H
-#define _ASM_BLACKFIN_CPUMASK_H
-
-#include <asm-generic/cpumask.h>
-
-#endif				/* _ASM_BLACKFIN_CPUMASK_H */