remoteproc: imx_dsp_rproc: Move imx_dsp_rproc_dcfg closer to imx_dsp_rproc_of_match

remoteproc: imx_dsp_rproc: Move imx_dsp_rproc_dcfg closer to imx_dsp_rproc_of_match

Move the imx_dsp_rproc_dcfg structure definitions closer to
imx_dsp_rproc_of_match to prepare for adding start/stop/detect_mode ops for
each i.MX variant.

Avoids the need to declare function prototypes such as
'static int imx_dsp_rproc_mbox_init(struct imx_dsp_rproc *priv)' at the
beginning of the file, improving code organization and readability.

No functional changes.

Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Daniel Baluta <daniel.baluta@nxp.com>
Reviewed-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Reviewed-by: Iuliana Prodan <iuliana.prodan@nxp.com>
Tested-by: Iuliana Prodan <iuliana.prodan@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Link: https://lore.kernel.org/r/20251119-imx-dsp-2025-11-19-v4-7-adafd342d07b@nxp.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>