ArmVirtPkg: 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
ArmVirtPkg.

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>

ArmVirtPkg/Library/NorFlashKvmtoolLib/NorFlashKvmtool.c

@@ -265,7 +265,7 @@ NorFlashPlatformLibConstructor (
       DEBUG ((
         DEBUG_ERROR,
         "%a: GetNodeProperty ('label') failed (Status == %r)\n",
-        __FUNCTION__,
+        __func__,
         Status
         ));
     } else if (AsciiStrCmp (Label, LABEL_UEFI_VAR_STORE) == 0) {
@@ -284,7 +284,7 @@ NorFlashPlatformLibConstructor (
       DEBUG ((
         DEBUG_ERROR,
         "%a: GetNodeProperty () failed (Status == %r)\n",
-        __FUNCTION__,
+        __func__,
         Status
         ));
       continue;