MdePkg: Change OPTIONAL keyword usage style

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3760

Update all use of ', OPTIONAL' to ' OPTIONAL,' for function params.

Cc: Andrew Fish <afish@apple.com>
Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Michael Kubacki <michael.kubacki@microsoft.com>
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>

MdePkg/Include/Protocol/HiiFont.h

@@ -447,7 +447,7 @@ EFI_STATUS
 (EFIAPI *EFI_HII_GET_FONT_INFO)(
   IN CONST  EFI_HII_FONT_PROTOCOL *This,
   IN OUT    EFI_FONT_HANDLE       *FontHandle,
-  IN CONST  EFI_FONT_DISPLAY_INFO *StringInfoIn, OPTIONAL
+  IN CONST  EFI_FONT_DISPLAY_INFO *StringInfoIn  OPTIONAL,
   OUT       EFI_FONT_DISPLAY_INFO **StringInfoOut,
   IN CONST  EFI_STRING            String OPTIONAL
 );
@@ -466,4 +466,3 @@ extern EFI_GUID gEfiHiiFontProtocolGuid;
 
 
 #endif
-