arch/tile: parameterize system PLs to support KVM port

While not a port to KVM (yet), this change modifies the kernel
to be able to build either at PL1 or at PL2 with a suitable
config switch.  Pushing up this change avoids handling branch
merge issues going forward with the KVM work.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
diff --git a/arch/tile/kernel/smp.c b/arch/tile/kernel/smp.c
index 1cb5ec7..75255d9 100644
--- a/arch/tile/kernel/smp.c
+++ b/arch/tile/kernel/smp.c
@@ -212,7 +212,7 @@
 
 		tile.x = cpu_x(cpu);
 		tile.y = cpu_y(cpu);
-		if (hv_get_ipi_pte(tile, 1, &pte) != 0)
+		if (hv_get_ipi_pte(tile, KERNEL_PL, &pte) != 0)
 			panic("Failed to initialize IPI for cpu %d\n", cpu);
 
 		offset = hv_pte_get_pfn(pte) << PAGE_SHIFT;