cellular: pseudomodem: Fix Python style issues in pseudomodem/

BUG=chromium:238809
TEST=Running ./utils/run_pylint.py inside the client/cros/cellular/pseudomodem
     directory should show no error messages.

Change-Id: I6848ceb6b9b5a0f59e0b1d3acbdfa4410fd1dfbb
Reviewed-on: https://gerrit.chromium.org/gerrit/50419
Commit-Queue: Arman Uguray <armansito@chromium.org>
Reviewed-by: Arman Uguray <armansito@chromium.org>
Tested-by: Arman Uguray <armansito@chromium.org>
18 files changed