x86/cpu/topology: Mop up primary thread mask handling

The early initcall to initialize the primary thread mask is not longer
required because topology_init_possible_cpus() can mark primary threads
correctly when initializing the possible and present map as the number of
SMT threads is already determined correctly.

The XENPV workaround is not longer required because XENPV now registers
fake APIC IDs which will just work like any other enumeration.

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/20240213210252.736104257@linutronix.de