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/Library/UefiLib/UefiLib.c

@@ -136,7 +136,7 @@ EfiCreateProtocolNotifyEvent(
   IN  EFI_GUID          *ProtocolGuid,
   IN  EFI_TPL           NotifyTpl,
   IN  EFI_EVENT_NOTIFY  NotifyFunction,
-  IN  VOID              *NotifyContext,  OPTIONAL
+  IN  VOID              *NotifyContext   OPTIONAL,
   OUT VOID              **Registration
   )
 {
@@ -207,7 +207,7 @@ EfiNamedEventListen (
   IN CONST EFI_GUID    *Name,
   IN EFI_TPL           NotifyTpl,
   IN EFI_EVENT_NOTIFY  NotifyFunction,
-  IN CONST VOID        *NotifyContext,  OPTIONAL
+  IN CONST VOID        *NotifyContext   OPTIONAL,
   OUT VOID             *Registration OPTIONAL
   )
 {