ElfReader: fix conditional free

buff cannot be zero.  Found by Coverity Scan, CID 25712.

Change-Id: Ibb411be376aab13832e3e5593fe001df1cbfc051

src/core/util/ElfReader.cc

@@ -105,8 +105,7 @@ void ElfReader::setup(const char* path) {
 			process_section(&sec_hdr, buff);
 		}
 	}
-	if (buff)
-		free(buff);
+	free(buff);
 
 	fclose(fp);