levelzero: add missing calloc return value check

[tkatila]

Static scan notified that calloc's return value wasn't checked.

[tkatila]

PS. There could be some define (e.g TEMP_ERROR_RET_VAL) in header for this magic value used (many times) in code: return -999.0;

That's a good point. I'll add it.

Sadly, Github's workers seem to be misbehaving today.