tee: optee: fix kernel-doc warnings

tee: optee: fix kernel-doc warnings

Fix kernel-doc issues in optee_private.h and optee_msg.h:

- Add missing documentation for struct members: optee_msg_param_value,
  optee_msg_param, optee_msg_arg, optee, and optee_ffa;
- Ensure member descriptions follow the order of declaration;
- Use consistent formatting (lowercase descriptions and ':' after
  member names);
- Adjust indentation for better alignment;

This resolves kernel-doc warnings such as missing member descriptions
and incorrect prototype documentation.
No functional changes.

Signed-off-by: Rodrigo Zaiden <rodrigoffzz@gmail.com>
Reviewed-by: Sumit Garg <sumit.garg@oss.qualcomm.com>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>