tools/x86/kcpuid: Refactor CPUID range handling for future expansion

tools/x86/kcpuid: Refactor CPUID range handling for future expansion

The kcpuid code assumes only two CPUID index ranges, standard (0x0...)
and extended (0x80000000...).

Since additional CPUID index ranges will be added in further commits,
replace the "is_ext" boolean with enumeration-based range classification.

Collect all CPUID ranges in a structured array and introduce helper
macros to iterate over it.  Use such helpers throughout the code.

Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20250324142042.29010-12-darwi@linutronix.de