drivers/ftdi: free allocated memory

Also uses calloc() for mpsse_ctx->write_buffer to prevent a false
positive valgrind report
"Syscall param ioctl(USBDEVFS_SUBMITURB).buffer points to uninitialised bytes(s)"

Change-Id: I91963371d15c21ea0fee4c40c1da86174db44520
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: http://openocd.zylin.com/4418
Tested-by: jenkins

src/jtag/drivers/ftdi.c

@@ -694,6 +694,18 @@ static int ftdi_quit(void)
 {
 	mpsse_close(mpsse_ctx);
 
+	struct signal *sig = signals;
+	while (sig) {
+		struct signal *next = sig->next;
+		free((void *)sig->name);
+		free(sig);
+		sig = next;
+	}
+
+	free(ftdi_device_desc);
+	free(ftdi_serial);
+	free(ftdi_location);
+
 	free(swd_cmd_queue);
 
 	return ERROR_OK;

src/jtag/drivers/mpsse.c

@@ -335,7 +335,13 @@ struct mpsse_ctx *mpsse_open(const uint16_t *vid, const uint16_t *pid, const cha
 	ctx->write_size = 16384;
 	ctx->read_chunk = malloc(ctx->read_chunk_size);
 	ctx->read_buffer = malloc(ctx->read_size);
-	ctx->write_buffer = malloc(ctx->write_size);
+
+	/* Use calloc to make valgrind happy: buffer_write() sets payload
+	 * on bit basis, so some bits can be left uninitialized in write_buffer.
+	 * Although this is perfectly ok with MPSSE, valgrind reports
+	 * Syscall param ioctl(USBDEVFS_SUBMITURB).buffer points to uninitialised byte(s) */
+	ctx->write_buffer = calloc(1, ctx->write_size);
+
 	if (!ctx->read_chunk || !ctx->read_buffer || !ctx->write_buffer)
 		goto error;