x86,cpuid: Consolidate native_cpuid and boot/cpuflags.c's cpuid

Currently, native_cpuid works in 32-bit non-PIC code and 64-bit PIC
code.  The cpuid function in arch/x86/boot/cpuflags.c works in
16-bit and 32-bit PIC and non-PIC code.

Consolidate them into a single implementation that works in all
compilation modes.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
3 files changed