arc64: Add port for Synopsys DesignWare ARCv3 ISA

arc64: Add port for Synopsys DesignWare ARCv3 ISA

Synopsys ARCv3 ISA includes 32-bit ARC HS5x targets and
64-bit ARC HS6x targets. Both CPU families are placed
in "arc64" subdirectories as it done for GCC port.
Target name arc64 is used for historical reasons and
Synopsys ARCv3 baremetal toolchains contain multilib
configurations both for 32-bit and 64-bit families.
arc32 target name is reserved for 32-bit ARC HS5x
targets in case of non-multilib 32-bit builds.

Note that libgloss libraries for ARCv3 are compatible with
libgloss for ARCv1/2. Thus, Makefile.inc for libgloss uses
sources from libgloss/arc directory except crtX.S files.

Co-authored-by: Shahab Vahedi <list@vahedi.org>
Co-authored-by: Claudiu Zissulescu <claziss@gmail.com>
Co-authored-by: Bruno Mauricio <brunoasmauricio@gmail.com>
Co-authored-by: Luis Silva <luis.m.silva99@hotmail.com>
Signed-off-by: Yuriy Kolerov <ykolerov@synopsys.com>