remoteproc: imx_dsp_rproc: use modern pm_ops

remoteproc: imx_dsp_rproc: use modern pm_ops

Without CONFIG_PM, the driver warns about unused functions:

drivers/remoteproc/imx_dsp_rproc.c:1210:12: error: 'imx_dsp_runtime_suspend' defined but not used [-Werror=unused-function]
 1210 | static int imx_dsp_runtime_suspend(struct device *dev)
      |            ^~~~~~~~~~~~~~~~~~~~~~~
drivers/remoteproc/imx_dsp_rproc.c:1178:12: error: 'imx_dsp_runtime_resume' defined but not used [-Werror=unused-function]
 1178 | static int imx_dsp_runtime_resume(struct device *dev)
      |            ^~~~~~~~~~~~~~~~~~~~~~

Change the old SET_SYSTEM_SLEEP_PM_OPS()/SET_RUNTIME_PM_OPS()
helpers to their modern replacements that avoid the warning,
and remove the now unnecessary __maybe_unused annotations
on the other PM helper functions.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com>
Reviewed-by: Iuliana Prodan <iuliana.prodan@nxp.com>
Link: https://lore.kernel.org/r/20230420213610.2219080-1-arnd@kernel.org
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>