Integrate meta-seconorth-machine/kirkstone-fix-boot-scr-test-cases

Commit: seco-ne/yocto/layers/meta-seconorth-machine@17c680aa

bootscript-uboot: fix test -z cases

"test -z $var" do not work correctly if var is not defined:

u-boot=> pri test u-boot=> if test -z test; then echo 123; fi u-boot=> if test -z "test"; then echo 123; fi 123 u-boot=>

Signed-off-by: Mikhail Vanyulin mikhail.vanyulin@rtsoft.de