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>

Currently, MIPS is the only architecture that needs
include/generated/asm-offsets.h, but we have got ./Kbuild file now.

It is a good reason to move asm-offsets.h rule from arch/mips/Makefile
to ./Kbuild and add dummy asm-offsets.c for the other architectures.
asm-offsets.h would be useful for all the architectures.

This commit does not implement include/generated/bounds.h,
but if necessary, it is easy to implement it.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>