x86/cpu: Remove unnecessary headers and reorder the rest

Remove the headers at intel.c that are no longer required.

Alphabetically reorder what remains since more headers will be included
in further commits.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20250304085152.51092-6-darwi@linutronix.de