u-boot-kirkwood: clone patch from openembedded-core, HYP-9203

This is just a hack to avoid a fetcher error.

The patch comes from
openembedded-core/meta/recipes-bsp/u-boot/files/0001-am335x_evm.h-Add-use-DEFAULT_LINUX_BOOT_ENV-environm.patch.

A proper solution should extend the FILESPATH in the right way.

Signed-off-by: Steffen Sledz <sledz@dresearch-fe.de>