MdeModulePkg: 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>

MdeModulePkg/Library/UefiBootManagerLib/BmLoadOption.c

@@ -476,7 +476,7 @@ EfiBootManagerInitializeLoadOption (
   IN  UINT32                            Attributes,
   IN  CHAR16                            *Description,
   IN  EFI_DEVICE_PATH_PROTOCOL          *FilePath,
-  IN  UINT8                             *OptionalData,   OPTIONAL
+  IN  UINT8                             *OptionalData    OPTIONAL,
   IN  UINT32                            OptionalDataSize
   )
 {