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/ptrace.h b/arch/tile/include/asm/ptrace.h
index 4a02bb0..ac6d343 100644
--- a/arch/tile/include/asm/ptrace.h
+++ b/arch/tile/include/asm/ptrace.h
@@ -62,8 +62,8 @@
 	pt_reg_t lr;		/* aliases regs[TREG_LR] */
 
 	/* Saved special registers. */
-	pt_reg_t pc;		/* stored in EX_CONTEXT_1_0 */
-	pt_reg_t ex1;		/* stored in EX_CONTEXT_1_1 (PL and ICS bit) */
+	pt_reg_t pc;		/* stored in EX_CONTEXT_K_0 */
+	pt_reg_t ex1;		/* stored in EX_CONTEXT_K_1 (PL and ICS bit) */
 	pt_reg_t faultnum;	/* fault number (INT_SWINT_1 for syscall) */
 	pt_reg_t orig_r0;	/* r0 at syscall entry, else zero */
 	pt_reg_t flags;		/* flags (see below) */