lz4: Mark unused lz4hc functions

This silences the following compiler warnings:

../lib/lz4/lz4hc_compress.c:619:13: warning: unused function 'LZ4_resetStreamHC' [-Wunused-function]
static void LZ4_resetStreamHC(LZ4_streamHC_t *LZ4_streamHCPtr, int compressionLevel)
            ^
../lib/lz4/lz4hc_compress.c:715:12: warning: unused function 'LZ4_compress_HC_continue' [-Wunused-function]
static int LZ4_compress_HC_continue(
           ^
../lib/lz4/lz4hc_compress.c:732:12: warning: unused function 'LZ4_saveDictHC' [-Wunused-function]
static int LZ4_saveDictHC(
           ^

Signed-off-by: Adam W. Willis <return.of.octobot@gmail.com>

lib/lz4/lz4hc_compress.c

@@ -616,7 +616,7 @@ EXPORT_SYMBOL(LZ4_compress_HC);
 /**************************************
  *	Streaming Functions
  **************************************/
-static void LZ4_resetStreamHC(LZ4_streamHC_t *LZ4_streamHCPtr, int compressionLevel)
+static void __maybe_unused LZ4_resetStreamHC(LZ4_streamHC_t *LZ4_streamHCPtr, int compressionLevel)
 {
 	LZ4_streamHCPtr->internal_donotuse.base = NULL;
 	LZ4_streamHCPtr->internal_donotuse.compressionLevel = (unsigned int)compressionLevel;
@@ -712,7 +712,7 @@ static int LZ4_compressHC_continue_generic(
 		inputSize, maxOutputSize, ctxPtr->compressionLevel, limit);
 }
 
-static int LZ4_compress_HC_continue(
+static int __maybe_unused LZ4_compress_HC_continue(
 	LZ4_streamHC_t *LZ4_streamHCPtr,
 	const char *source,
 	char *dest,
@@ -729,7 +729,7 @@ static int LZ4_compress_HC_continue(
 
 /* dictionary saving */
 
-static int LZ4_saveDictHC(
+static int __maybe_unused LZ4_saveDictHC(
 	LZ4_streamHC_t *LZ4_streamHCPtr,
 	char *safeBuffer,
 	int dictSize)