MdeModulePkg: 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
MdeModulePkg.

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>

MdeModulePkg/Core/Pei/FwVol/FwVol.c

@@ -1494,7 +1494,7 @@ ProcessFvFile (
       DEBUG ((
         DEBUG_INFO,
         "%a() FV at 0x%x, FvAlignment required is 0x%x\n",
-        __FUNCTION__,
+        __func__,
         FvHeader,
         FvAlignment
         ));