x86/acpi/cstate: Improve Intel Family model checks

Update the Intel Family checks to consistently use Family 15 instead of
Family 0xF. Also, get rid of one of last usages of x86_model by using
the new VFM checks.

Update the incorrect comment since the check has changed since the
initial commit:

  ee1ca48f ("ACPI: Disable ARB_DISABLE on platforms where it is not needed")

The two changes were:

 - 3e2ada58 ("ACPI: fix Compaq Evo N800c (Pentium 4m) boot hang regression")
   removed the P4 - Family 15.

 - 03a05ed1 ("ACPI: Use the ARB_DISABLE for the CPU which model id is less than 0x0f.")
   got rid of CORE_YONAH - Family 6, model E.

Signed-off-by: Sohil Mehta <sohil.mehta@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20250219184133.816753-9-sohil.mehta@intel.com