Commit cbb38440 ("meta-digi-dey: sysinfo: Add chip revision sysinfo output")
introduced a new script variable to determine the SOC revision of the module.
However this entry only is available on the CC8X platforms. This commit checks
if the entry exist and then tries to read it to avoid unexpected issues with
devices without this entry.
https://jira.digi.com/browse/DEL-7263
Signed-off-by: Arturo Buzarra <arturo.buzarra@digi.com>