kvm/i386: fix return values of is_host_cpu_intel()

kvm/i386: fix return values of is_host_cpu_intel()

is_host_cpu_intel() should return TRUE if the host cpu in Intel based, otherwise
it should return FALSE. Currently, it returns zero (FALSE) when the host CPU
is INTEL and non-zero otherwise. Fix the function so that it agrees more with
the semantics. Adjust the calling logic accordingly. RAPL needs Intel host cpus.
If the host CPU is not Intel baseed, we should report error.

Signed-off-by: Ani Sinha <anisinha@redhat.com>
Link: https://lore.kernel.org/r/20240903080004.33746-1-anisinha@redhat.com
[While touching the code remove too many spaces from the second part of the
 error. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>