remoteproc: imx_rproc: Clean up after ops introduction

remoteproc: imx_rproc: Clean up after ops introduction

With the switch-case in imx_rproc_{start,stop}{} removed, simplify
the code logic by removing 'goto'. The last switch-case in
imx_rproc_detect_mode() are no longer needed and can be removed.

This cleanup improves code readability and aligns with the new ops-based
design.

No functional changes.

Reviewed-by: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Link: https://lore.kernel.org/r/20250910-imx-rproc-cleanup-v2-6-10386685b8a9@nxp.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>