Attest: Align code to TF-M code-style

`coding_guide.rst` mentions:
- In the switch statement, aligned cases with the switch keyword.

Use correct doxygen format for parameters that can be an input or an
output.

Change-Id: Ib30e07192dfd8970cfbaa5194bc397ca8b6db835
Signed-off-by: Mudit Sharma <mudit.sharma@arm.com>
2 files changed