ARM: includecheck fix: atomic.h

fix the following 'make includecheck' warning:

  arch/arm/include/asm/atomic.h: asm/system.h is included more than once.
Signed-off-by: NJaswinder Singh Rajput <jaswinderrajput@gmail.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/atomic.h

@@ -159,8 +159,6 @@ static inline void atomic_clear_mask(unsigned long mask, unsigned long *addr)
 
 #else /* ARM_ARCH_6 */
 
-#include <asm/system.h>
-
 #ifdef CONFIG_SMP
 #error SMP not supported on pre-ARMv6 CPUs
 #endif