olimex_a20_olinuxino_lime2: bump U-Boot to 2016.05
The patch fixes build by GCC 5 (unsupported by the older U-Boot).
Signed-off-by: Jan Viktorin <viktorin@rehivetech.com>
Reported-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>