The early argument of x86_init::mpparse::get_smp_config() is more than
confusing. Provide two callbacks, one for each purpose.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240212154639.370491894@linutronix.de