shell: modules: kernel: streamline code

This commit includes cleanups to `kernel_service`:
- `shell_tdata_dump()`:
  Adjust formatting to align with `.clang-format`.
- `shell_stack_dump()`:
  Update to pass `sh` directly instead of `user_data` since
  it is already assigned.

Signed-off-by: Pisit Sawangvonganan <pisit@ndrsolution.com>