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/include/asm/system.h b/arch/tile/include/asm/system.h
index fb7ff95..5388850 100644
--- a/arch/tile/include/asm/system.h
+++ b/arch/tile/include/asm/system.h
@@ -164,7 +164,7 @@
 /* Helper function for _switch_to(). */
 extern struct task_struct *__switch_to(struct task_struct *prev,
 				       struct task_struct *next,
-				       unsigned long new_system_save_1_0);
+				       unsigned long new_system_save_k_0);
 
 /* Address that switched-away from tasks are at. */
 extern unsigned long get_switch_to_pc(void);