ArmPlatformPkg: Update code to be more C11 compliant by using __func__

__FUNCTION__ is a pre-standard extension that gcc and Visual C++ among
others support, while __func__ was standardized in C99.

Since it's more standard, replace __FUNCTION__ with __func__ throughout
ArmPlatformPkg.

Signed-off-by: Rebecca Cran <rebecca@bsdio.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>

ArmPlatformPkg/Drivers/SP805WatchdogDxe/SP805Watchdog.c

@@ -397,7 +397,7 @@ SP805Initialize (
       DEBUG ((
         DEBUG_ERROR,
         "%a: failed to register watchdog interrupt - %r\n",
-        __FUNCTION__,
+        __func__,
         Status
         ));
       return Status;
@@ -406,7 +406,7 @@ SP805Initialize (
     DEBUG ((
       DEBUG_WARN,
       "%a: no interrupt specified, running in RESET mode only\n",
-      __FUNCTION__
+      __func__
       ));
   }