arc: add architecture header files

arc: add architecture header files

These are header files used by ARC700 architecture.

Also note that "arch-arc700/hardware.h" is only required for compilation of
"designware_i2c" driver which refers to "asm/arch/hardware.h".
It would be good to fix mentioned driver sometime soon but it will cause
changes in ARM board configs that use "designware_i2c".

Signed-off-by: Alexey Brodkin <[email protected]>
Cc: Vineet Gupta <[email protected]>
Cc: Francois Bedard <[email protected]>
Cc: Wolfgang Denk <[email protected]>
Cc: Heiko Schocher <[email protected]>