[U-Boot] [ANN] U-Boot v2017.09-rc3 released

Hey all,

It's release day and v2017.09-rc3 is out. I think there's still a few outstanding important bugfixes that need to come in, and probably a few more Kconfig migrations as well.

If anyone has critical fixes I've missed please speak up. I think I've got an idea on what they are but never the less, better to speak up now than assume i saw it.

Things look on track for rc4 on the 4th of September and then a final release on the 11th.. Thanks all!