Enable Debug and SError exceptions on warm boot path

Enable Debug and SError exceptions:
 - when receiving an SMC;
 - when a CPU is physically powered up (upon resumption from suspend
   or in response to a PSCI cpu_on call)

Change-Id: I7e5613e34034be6ed68ec9e2aef4de66aa5ac65e

bl31/aarch64/runtime_exceptions.S

@@ -44,6 +44,12 @@
 	 * -----------------------------------------------------
 	 */
 	.macro	handle_sync_exception
+	/* ---------------------------------------------
+	 * Enable Debug and SError interrupts
+	 * ---------------------------------------------
+	 */
+	msr	daifclr, #(DAIF_ABT_BIT | DAIF_DBG_BIT)
+
 	str	x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR]
 	mrs	x30, esr_el3
 	ubfx	x30, x30, #ESR_EC_SHIFT, #ESR_EC_LENGTH

services/std_svc/psci/psci_entry.S

@@ -70,6 +70,12 @@ psci_aff_common_finish_entry:
 	msr	vbar_el3, x0
 	isb
 
+	/* ---------------------------------------------
+	 * Enable Debug and SError interrupts
+	 * ---------------------------------------------
+	 */
+	msr	daifclr, #(DAIF_ABT_BIT | DAIF_DBG_BIT)
+
 	/* ---------------------------------------------
 	 * Use SP_EL0 for the C runtime stack.
 	 * ---------------------------------------------