x86: make (early)_identify_cpu more the same between 32bit and 64 bit

1. add extended_cpuid_level for 32bit
 2. add generic_identify for 64bit
 3. add early_identify_cpu for 32bit
 4. early_identify_cpu not be called by identify_cpu
 5. remove early in get_cpu_vendor for 32bit
 6. add get_cpu_cap
 7. add cpu_detect for 64bit

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>