lz4: do not export static symbol

Kbuild now complains (rightly) about it.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/lz4/lz4hc_compress.c

@@ -663,7 +663,6 @@ static void LZ4HC_setExternalDict(
 	/* match referencing will resume from there */
 	ctxPtr->nextToUpdate = ctxPtr->dictLimit;
 }
-EXPORT_SYMBOL(LZ4HC_setExternalDict);
 
 static int LZ4_compressHC_continue_generic(
 	LZ4_streamHC_t *LZ4_streamHCPtr,