Remove x86-specific instructions from telnet server

telnetsrv uses the Intel/AMD-specific "cpuid" instruction, which is not available on ARM machines. Remove the call.

The previous code was checking for the number of cores, which is retained by a call to get_nprocs(). I did not find an equivalent for the number of threads in C. In C++, there would be https://en.cppreference.com/w/cpp/thread/thread/hardware_concurrency, in case it's relevant for anybody.

also, add it to the cross-compilation pipeline