NetworkPkg: 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: Maciej Rabeda <maciej.rabeda@linux.intel.com>

NetworkPkg/Ip4Dxe/Ip4Option.c

@@ -115,7 +115,7 @@ Ip4CopyOption (
   IN     UINT8              *Option,
   IN     UINT32             OptionLen,
   IN     BOOLEAN            FirstFragment,
-  IN OUT UINT8              *Buf,           OPTIONAL
+  IN OUT UINT8              *Buf            OPTIONAL,
   IN OUT UINT32             *BufLen
   )
 {

NetworkPkg/Ip4Dxe/Ip4Option.h

@@ -60,7 +60,7 @@ Ip4CopyOption (
   IN     UINT8              *Option,
   IN     UINT32             OptionLen,
   IN     BOOLEAN            FirstFragment,
-  IN OUT UINT8              *Buf,           OPTIONAL
+  IN OUT UINT8              *Buf            OPTIONAL,
   IN OUT UINT32             *BufLen
   );
 #endif