x86/mm/32: Load a sane CR3 before cpu_init() on secondary CPUs

For unknown historical reasons (i.e. Borislav doesn't recall),
32-bit kernels invoke cpu_init() on secondary CPUs with
initial_page_table loaded into CR3.  Then they set
current->active_mm to &init_mm and call enter_lazy_tlb() before
fixing CR3.  This means that the x86 TLB code gets invoked while CR3
is inconsistent, and, with the improved PCID sanity checks I added,
we warn.

Fix it by loading swapper_pg_dir (i.e. init_mm.pgd) earlier.

Reported-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reported-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 72c0098d

 ("x86/mm: Reinitialize TLB state on hotplug and resume")
Link: http://lkml.kernel.org/r/30cdfea504682ba3b9012e77717800a91c22097f.1505663533.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>