[U-Boot] storage support for ub_dev_write API function

Hi All!

I have stumbled upon the lack of support for storage devices in API's ub_dev_write()/API_dev_write() functions. Currently the function supports only the network devices.

I have implemented the support for the storage by adapting the code from API_dev_read() function, and added the ub_dev_write() to the glue.c. Interface for the network devices is unchanged.

I could only test the ub_dev_write() for storage, but my application doesn't use the ub_dev_send() thus I can't test it (but 99% sure that it still works).

The patch is attached (should apply cleanly to the current git master git.denx.de/u-boot.git).

Comments are welcome. Applying it to the git master is even more so.