Port SMCCC code from Linux kernel. To accomodate that:

  - Introduce CONFIG_ARM_SMCCC, to allow enabling the code
    independent of CONFIG_ARM_SECURE_MONITOR

  - Bring <linux/arm-smccc.h> in

  - Add necessary constants to arch/arm/asm-offsets.c

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>