i386: kvm: kvm_arch_get_supported_cpuid: move R_EDX hack outside of for loop

The for loop will become a separate function, so clean it up so it can
become independent from the bit hacking for R_EDX.

No behavior change[1], just code movement.

[1] Well, only if the kernel returned CPUID leafs 1 or 0x80000001 as
    unsupported, but there's no kernel version that does that.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
