Hello.
configuration files produced by petalinux. The better way to make these changes is to run the corresponding petalinux command and make changes in the interface. For example
run "petalinux-config -c u-boot" command, which open the u-boot configuration interface and use the "/" key to run options search (or find needed options in menu) and then
change variable value.
Best regards
Oleksandr Kiyenko