remoteproc: imx_dsp_rproc: Convert to dev_pm_domain_attach|detach_list()

Let's avoid the boilerplate code to manage the multiple PM domain case, by
converting into using dev_pm_domain_attach|detach_list().

Cc: Bjorn Andersson <andersson@kernel.org>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Daniel Baluta <daniel.baluta@nxp.com>
Cc: <linux-remoteproc@vger.kernel.org>
Tested-by: Iuliana Prodan <iuliana.prodan@nxp.com>
Reviewed-by: Iuliana Prodan <iuliana.prodan@nxp.com>
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20240130123951.236243-3-ulf.hansson@linaro.org