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/Library/PiDxeS3BootScriptLib/BootScriptSave.c

@@ -579,7 +579,7 @@ S3BootScriptLibDeinitialize (
     return RETURN_SUCCESS;
   }
 
-  DEBUG ((DEBUG_INFO, "%a() in %a module\n", __FUNCTION__, gEfiCallerBaseName));
+  DEBUG ((DEBUG_INFO, "%a() in %a module\n", __func__, gEfiCallerBaseName));
 
   if (mEventDxeSmmReadyToLock != NULL) {
     //