[alert_handler] Update chip_sw_lpg_clkoff_test
[alert_handler] Update chip_sw_lpg_clkoff_test

    Added the previously removed Phase #2 to code to test the fatal alerts.

    Check the discussion here
    https://github.com/lowRISC/opentitan/pull/14858#discussion_r995129415

Signed-off-by: Bilgiday Yuce <78fdfcc7b6a794362d01e4250046b509d0579329@google.com>

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