remoteproc: imx_rproc: Use devm_rproc_add() helper

remoteproc: imx_rproc: Use devm_rproc_add() helper

Replace manual rproc_add() and cleanup logic with devm_rproc_add(), which
ties the remoteproc lifecycle to the device's lifecycle. This simplifies
error handling and ensures proper cleanup.

With no need to invoke rproc_del(), the remove() ops could be removed.

No functional changes.

Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Link: https://lore.kernel.org/r/20250926-imx_rproc_v3-v3-6-4c0ec279cc5f@nxp.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>