utils/genrandconfig: fix flake8 warnings

Fixes:

utils/genrandconfig:369:17: E231 missing whitespace after ','
utils/genrandconfig:370:1: E101 indentation contains mixed spaces and tabs
utils/genrandconfig:370:1: W191 indentation contains tabs
utils/genrandconfig:372:1: E101 indentation contains mixed spaces and tabs

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>