SecurityPkg: 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: Jian J Wang <jian.j.wang@intel.com>

SecurityPkg/RandomNumberGenerator/RngDxe/Rand/RngDxe.c

@@ -49,7 +49,7 @@ EFI_STATUS
 EFIAPI
 RngGetRNG (
   IN EFI_RNG_PROTOCOL            *This,
-  IN EFI_RNG_ALGORITHM           *RNGAlgorithm, OPTIONAL
+  IN EFI_RNG_ALGORITHM           *RNGAlgorithm  OPTIONAL,
   IN UINTN                       RNGValueLength,
   OUT UINT8                      *RNGValue
   )