arc: add support of exceptions

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
arc: zero .bss section on early init and copy it during relocation

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
arc: correctly preserve critical values for invocation of C function

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
arc: in debug build stop on break-point instead of reset

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