axs103: Support slave core kick-start on axs103 v1.1 firmware

In axs103 v1.1 procedure to kick-start slave cores has changed quite a bit
compared t previous implementation.

In particular:
 * We used to have a generic START bit for all cores selected by CORE_SEL
   mask. But now we don't touch CORE_SEL at all because we have a dedicated
   START bit for each core:
     bit 0: Core 0 (master)
     bit 1: Core 1 (slave)
 * Now there's no need to select "manual" mode of core start

Additional challenge for us is how to tell which axs103 firmware we're
dealing with. For now we'll rely on ARC core version which was bumped
from 2.1c to 3.0.

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