arc770: use generic 02_sysinfo

arc770: use generic 02_sysinfo

Currently arc770 sets a board name from compatible for no apparent
reason. Just use the compatible directly instead.

This theoretically removes a board name "generic" when no compatible
was present, however, there is no case where this "generic" board
name was actually used.

This also fixes an issue where snps,axs101 would not have been
properly detected anyway, as its case was not set up syntactically
correct.

Fixes: 576621f1e353 ("linux: add support of Synopsys ARC770-based boards")
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>