fix error when parsing ppc64 models on x86 host

fix error when parsing ppc64 models on x86 host

When parsing ppc64 models on an x86 host an out-of-memory error message is displayed due
to it checking for retcpus being NULL. Fix this by removing the check whether retcpus is NULL
since we will realloc into this variable.
Also in the X86 model parser display the OOM error at the location where it happens.