[meta-xilinx] Recipe for u-boot 2015.1

[Philip Balister]

I've made a recipe for u-boot 2015.1 for testing from u-boot-xlnx. I
gather this is very close to mainline u-boot. Is there any interest in
an updates u-boot, or is this in process already?

On a related note, could we enable saving the environment to the SD card
(for sd card cases) and turn on some of the boot harder options in case
of bogus characters on the serial port?

Philip