plat/arm: Fix ARM_INSTANTIATE_LOCK syntax anomaly

The current definition of ARM_INSTANTIATE_LOCK macro includes a
semicolon, which means it's omitted where it's used. This is anomalous
for a C statement in global scope.

Fix this by removing semicolon from the definition; and where it's a
NOP, declare a file-scoped variable explicitly tagged as unused to avoid
compiler warning.

No functional changes.

Change-Id: I2c1d92ece4777e272a025011e03b8003f3543335
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
diff --git a/plat/arm/board/fvp/drivers/pwrc/fvp_pwrc.c b/plat/arm/board/fvp/drivers/pwrc/fvp_pwrc.c
index 9dad146..5948e14 100644
--- a/plat/arm/board/fvp/drivers/pwrc/fvp_pwrc.c
+++ b/plat/arm/board/fvp/drivers/pwrc/fvp_pwrc.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2016, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2017, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -15,7 +15,7 @@
  * TODO: Someday there will be a generic power controller api. At the moment
  * each platform has its own pwrc so just exporting functions is fine.
  */
-ARM_INSTANTIATE_LOCK
+ARM_INSTANTIATE_LOCK;
 
 unsigned int fvp_pwrc_get_cpu_wkr(u_register_t mpidr)
 {