arc: Pass proper CPU value to the disassembler

arc: Pass proper CPU value to the disassembler

There was a problem with generation of the disassembler options for ARC in GDB,
because a BFD architecture name was used as a CPU name, but they have different
meaning even if some architectures have same name as respective CPUs.  Target
description specifies a BFD architecture, which is different from ARC CPU, as
accepted by the disassembler (and most other ARC tools), because CPU values are
much more fine grained - there can be multiple CPU values per single BFD
architecture.  As a result this code should translate architecture to some CPU
value.  Since there is no info on exact CPU configuration, it is best to use
the most feature-rich CPU, so that the disassembler will recognize all
instructions available to the specified architecture.

gdb/ChangeLog
yyyy-mm-dd  Anton Kolesov  <Anton.Kolesov@synopsys.com>

	* arc-tdep.c (arc_gdbarch_init): Pass proper cpu value to disassembler.
	* arc-tdep.h (arc_arch_is_em): New function.
	(arc_arch_is_hs): Likewise.

gdb/testsuite/ChangeLog
yyyy-mm-dd  Anton Kolesov  <Anton.Kolesov@synopsys.com>

	* gdb.arch/arc-tdesc-cpu.exp: New file.
	* gdb.arch/arc-tdesc-cpu.xml: Likewise.