PSCI: Fix MISRA defects in MEM_PROTECT

MISRA C-2012 Rules 10.1 and 10.3.

Change-Id: I88cd5f56cda5780f2e0ba541c0f5b561309ab3af
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/lib/psci/psci_private.h b/lib/psci/psci_private.h
index ac99876..75f7d45 100644
--- a/lib/psci/psci_private.h
+++ b/lib/psci/psci_private.h
@@ -330,7 +330,7 @@
 			unsigned int power_state);
 
 /* Private exported functions from psci_mem_protect.c */
-int psci_mem_protect(unsigned int enable);
-int psci_mem_chk_range(uintptr_t base, u_register_t length);
+u_register_t psci_mem_protect(unsigned int enable);
+u_register_t psci_mem_chk_range(uintptr_t base, u_register_t length);
 
 #endif /* PSCI_PRIVATE_H */