arm-io: Panic in case of io setup failure

Currently, an IO setup failure will be ignored on arm platform release
build. Change this to panic instead.

Change-Id: I027a045bce2422b0a0fc4ff9e9d4c6e7bf5d2f98
Signed-off-by: Louis Mayencourt <louis.mayencourt@arm.com>
diff --git a/include/plat/arm/common/plat_arm.h b/include/plat/arm/common/plat_arm.h
index 4751314..025a64f 100644
--- a/include/plat/arm/common/plat_arm.h
+++ b/include/plat/arm/common/plat_arm.h
@@ -149,7 +149,7 @@
 #define ARM_ROTPK_DEVEL_ECDSA_ID	3
 
 /* IO storage utility functions */
-void arm_io_setup(void);
+int arm_io_setup(void);
 
 /* Security utility functions */
 void arm_tzc400_setup(const arm_tzc_regions_info_t *tzc_regions);