Fix MISRA rule 8.4 in common code

Rule 8.4: A compatible declaration shall be visible when
          an object or function with external linkage is defined.

Change-Id: I26e042cb251a6f9590afa1340fdac73e42f23979
Signed-off-by: Roberto Vargas <roberto.vargas@arm.com>
diff --git a/services/arm_arch_svc/arm_arch_svc_setup.c b/services/arm_arch_svc/arm_arch_svc_setup.c
index eedac86..a809c42 100644
--- a/services/arm_arch_svc/arm_arch_svc_setup.c
+++ b/services/arm_arch_svc/arm_arch_svc_setup.c
@@ -33,7 +33,7 @@
 /*
  * Top-level Arm Architectural Service SMC handler.
  */
-uintptr_t arm_arch_svc_smc_handler(uint32_t smc_fid,
+static uintptr_t arm_arch_svc_smc_handler(uint32_t smc_fid,
 	u_register_t x1,
 	u_register_t x2,
 	u_register_t x3,