[bazel] Use get_lc_items() for ROM e2e targets
[bazel] Use get_lc_items() for ROM e2e targets

This avoids ~100 calls to the string `.lower()` method.

Signed-off-by: Dan McArdle <8fb240f11ec935676fcfd8aed04f42f9ee63efa8@google.com>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan