tile: support CONFIG_PREEMPT

This change adds support for CONFIG_PREEMPT (full kernel preemption).
In addition to the core support, this change includes a number
of places where we fix up uses of smp_processor_id() and per-cpu
variables.  I also eliminate the PAGE_HOME_HERE and PAGE_HOME_UNKNOWN
values for page homing, as it turns out they weren't being used.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

arch/tile/kernel/sys.c

@@ -38,8 +38,10 @@
 SYSCALL_DEFINE3(cacheflush, unsigned long, addr, unsigned long, len,
 		unsigned long, flags)
 {
+	/* DCACHE is not particularly effective if not bound to one cpu. */
 	if (flags & DCACHE)
-		homecache_evict(cpumask_of(smp_processor_id()));
+		homecache_evict(cpumask_of(raw_smp_processor_id()));
+
 	if (flags & ICACHE)
 		flush_remote(0, HV_FLUSH_EVICT_L1I, mm_cpumask(current->mm),
 			     0, 0, 0, NULL, NULL, 0);