xtensa: add SMP support

This is largely based on SMP code from the xtensa-2.6.29-smp tree by
Piet Delaney, Marc Gauthier, Joe Taylor, Christian Zankel (and possibly
other Tensilica folks).

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

arch/xtensa/mm/mmu.c

@@ -22,7 +22,7 @@ void __init paging_init(void)
 /*
  * Flush the mmu and reset associated register to default values.
  */
-void __init init_mmu(void)
+void init_mmu(void)
 {
 #if !(XCHAL_HAVE_PTP_MMU && XCHAL_HAVE_SPANNING_WAY)
 	/*
@@ -37,7 +37,7 @@ void __init init_mmu(void)
 	set_itlbcfg_register(0);
 	set_dtlbcfg_register(0);
 #endif
-	flush_tlb_all();
+	local_flush_tlb_all();
 
 	/* Set rasid register to a known value. */