dfu: Add optional timeout parameter

When the `dfu` command is called from the U-Boot environment,
it now accepts an optional parameter that specifies a timeout (in seconds).
If a DFU connection is not made within that time the `dfu` command exits
(as it would if Ctrl+C was pressed). If the timeout is left empty or being
zero the `dfu` command behaves as it does now.

This is useful for allowing U-Boot to check to see if anything wants to
upload new firmware before continuing to boot.

The patch is based on the commit
https://github.com/01org/edison-u-boot/commit/5e966ccc3c65c18c9783741fa04e0c45e021780c
by Sebastien Colleur, which has been heavily reworked due to U-Boot changes
in the past.

Signed-off-by: Brad Campbell <bradjc5@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
diff --git a/include/dfu.h b/include/dfu.h
index 2e3e91c..fb5260d 100644
--- a/include/dfu.h
+++ b/include/dfu.h
@@ -178,6 +178,11 @@
 unsigned long dfu_get_buf_size(void);
 bool dfu_usb_get_reset(void);
 
+#ifdef CONFIG_DFU_TIMEOUT
+unsigned long dfu_get_timeout(void);
+void dfu_set_timeout(unsigned long);
+#endif
+
 int dfu_read(struct dfu_entity *de, void *buf, int size, int blk_seq_num);
 int dfu_write(struct dfu_entity *de, void *buf, int size, int blk_seq_num);
 int dfu_flush(struct dfu_entity *de, void *buf, int size, int blk_seq_num);