[ARC] Add arc-cpu.def with processor definitions

[ARC] Add arc-cpu.def with processor definitions

This patch extracts ARC CPU definitions from gas/config/tc-arc.c (cpu_types)
into a separate file arc-cpu.def.  This will allow reuse of CPU type definition
in multiple places where it might be needed, for example in disassembler.  This
will help ensure that gas and disassembker use same option values for CPUs.

arc-cpu.def file relies on preprocessor macroses which are defined somewhere
else.  This for example multiple C files to include arc-cpu.def, but define
different macroses, therefore creating different structures.

include/ChangeLog:
yyyy-mm-dd  Anton Kolesov  <anton.kolesov@synopsys.com>

	* elf/arc-cpu.def: New file.

gas/ChangeLog:
yyyy-mm-dd  Anton Kolesov  <anton.kolesov@synopsys.com>

	* config/tc-arc.c (cpu_types): Include arc-cpu.def

Signed-off-by: Anton Kolesov <Anton.Kolesov@synopsys.com>