[U-Boot] [ANN] U-Boot v2017.05-rc3 released

Hey all,

It's release day and v2017.05-rc3 is out. Most of the changes from -rc2 to -rc3 are Kconfig migrations, and I'm happy with that. I also re-synced the defconfig files and CONFIG symbol whitelist.

If anyone has critical fixes I've missed, or some other Kconfig changes (that I can prove out as correct), please speak up.

As a final note, I expect us to release v2017.05 on schedule on the 8th of May.

Thanks all!