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/mm/init.c b/arch/tile/mm/init.c
index d89c9ea..78e1982 100644
--- a/arch/tile/mm/init.c
+++ b/arch/tile/mm/init.c
@@ -1060,7 +1060,7 @@
 
 	/*
 	 * Free the pages mapped from 0xc0000000 that correspond to code
-	 * pages from 0xfd000000 that we won't use again after init.
+	 * pages from MEM_SV_INTRPT that we won't use again after init.
 	 */
 	free_init_pages("unused kernel text",
 			(unsigned long)_sinittext - text_delta,