net/asterisk20: Fix Endianness detection

After update to 20.16.0 and 22.6.0 Asterisk misbehaves, see
https://github.com/asterisk/asterisk/issues/1536
The patch submitted in https://github.com/asterisk/asterisk/pull/1541
fixes that.

PR: 290317 290318
Reported by: Oleksandr Kryvulia <o.kryvulia@flex-it.com.ua> (maintainer)