MdeModulePkg: Fix MSFT C4255 warning

V2:
Fix MSFT C4255 warning
V1:
Enable MSFT C4255 warning.

From MSDN:
Compiler Warning (level 4) C4255
function' : no function prototype given: converting '()' to '(void)'
The compiler did not find an explicit list of arguments to a function.
This warning is for the C compiler only.

Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Bell Song <binx.song@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

MdeModulePkg/Include/Library/PlatformVarCleanupLib.h

@@ -32,6 +32,7 @@ typedef enum {
 VAR_ERROR_FLAG
 EFIAPI
 GetLastBootVarErrorFlag (
+  VOID
   );
 
 /**