clang requires that.

In file included from arch/x86/cpu.c:9:
arch/x86/include/asm/bitops.h:24:15: error: ambiguous instructions
require an explicit suffix (could be 'btsw', 'btsl', or 'btsq')
        asm volatile("bts %1,%0" : ADDR : "Ir" (nr) : "memory");
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>