MdeModulePkg BrotliLib: Rename function with the specific lib name

This change is to avoid the function conflict.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Liming Gao <liming.gao@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
(cherry picked from commit 792ace0ac3)

MdeModulePkg/Library/BrotliCustomDecompressLib/BrotliDecompressLibInternal.h

@@ -3,7 +3,7 @@
 
   Allows BROTLI code to build under UEFI (edk2) build environment
 
-  Copyright (c) 2017, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2017 - 2018, Intel Corporation. All rights reserved.<BR>
   This program and the accompanying materials
   are licensed and made available under the terms and conditions of the BSD License
   which accompanies this distribution.  The full text of the license may be found at
@@ -41,12 +41,12 @@ typedef struct
 #define memset(dest,ch,count)       SetMem(dest,(UINTN)(count),(UINT8)(ch))
 
 VOID *
-malloc (
+BrDummyMalloc (
   IN size_t   Size
   );
 
 VOID
-free (
+BrDummyFree (
   IN VOID *   Ptr
   );