Apply pylint to conv_linker_config.py

1. Run pyformat scripts/conv_linker_config.py -s 4 --force_quote_type none -i to fix formatting
2. Annotate #pylint: disable=import-error for linker_config_pb2 since it
will be provided by soong

Test: m conv_linker_config
Test: pylint --rcfile tools/repohooks/tools/pylintrc
build/soong/scripts/conv_linker_config.py
Bug: 195738175

Change-Id: I791576cf65cb053f68c804f8ec5c2fc22976fdb4