gitignore: update the list of compliance generated files

Update the list of compliance generated txt files and sort the list
while we are at it.

$ ./scripts/ci/check_compliance.py -l | sort
BinaryFiles
Checkpatch
DevicetreeBindings
Gitlint
Identity
ImageSize
Kconfig
KconfigBasic
MaintainersFormat
Nits
Pylint
YAMLLint

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>