x86: do tests before do_boot_cpu in i386

Do tests before do_boot_cpu in native_cpu_up for i386.
Tests are a little bit broader than originally, and are the
same as x86_64. Test for smp_callin is not applicable right now
and is deferred.

Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>