arm64: Provide a namespace to NCAPS

Building arm64.allmodconfig leads to the following warning:

usb/gadget/function/f_ncm.c:203:0: warning: "NCAPS" redefined
 #define NCAPS (USB_CDC_NCM_NCAP_ETH_FILTER | USB_CDC_NCM_NCAP_CRC_MODE)
 ^
In file included from /home/build/work/batch/arch/arm64/include/asm/io.h:32:0,
                 from /home/build/work/batch/include/linux/clocksource.h:19,
                 from /home/build/work/batch/include/clocksource/arm_arch_timer.h:19,
                 from /home/build/work/batch/arch/arm64/include/asm/arch_timer.h:27,
                 from /home/build/work/batch/arch/arm64/include/asm/timex.h:19,
                 from /home/build/work/batch/include/linux/timex.h:65,
                 from /home/build/work/batch/include/linux/sched.h:19,
                 from /home/build/work/batch/arch/arm64/include/asm/compat.h:25,
                 from /home/build/work/batch/arch/arm64/include/asm/stat.h:23,
                 from /home/build/work/batch/include/linux/stat.h:5,
                 from /home/build/work/batch/include/linux/module.h:10,
                 from /home/build/work/batch/drivers/usb/gadget/function/f_ncm.c:19:
arch/arm64/include/asm/cpufeature.h:27:0: note: this is the location of the previous definition
 #define NCAPS     2

So add a ARM64 prefix to avoid such problem.

Reported-by: Olof's autobuilder <build@lixom.net>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>