[ci] Use consistent style in azure-pipelines.yml
[ci] Use consistent style in azure-pipelines.yml

These changes include:
- Consistent quotation (single quotes in YAML, only for multi-word
  strings; double-quotes in bash around all variable references).
- Consistent use of [[ instead of [ for testing conditions.
- Consistent indentation within bash.
- Consistent file paths (e.g., when calling a script, prefix with ./
  only when strictly necessary).

Signed-off-by: Miguel Young de la Sota <71b8e7f4945fd97b98544cf897992af89646547a@google.com>

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