buildroot

configs/amarula_vyasa_rk3288: uboot needs pylibfdt

For this platform, u-boot uses dtoc during the build, which needs Python
libfdt. Set the corresponding option TARGET_UBOOT_NEEDS_PYLIBFDT in the
defconfig.

Signed-off-by: Vincent Stehlé <vincent.stehle@laposte.net>
Cc: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>