uboot-imx

arc: merge common start-up code between ARC and ARCv2

Even though ARCompact and ARCv2 are not binary compatible most of
assembly instructions are used in both. With this change we'll get rid
of duplicate code.

Still IVTs are implemented differently so we're keeping them in separate
files.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>