remoteproc: imx_rproc: Move imx_rproc_dcfg closer to imx_rproc_of_match

remoteproc: imx_rproc: Move imx_rproc_dcfg closer to imx_rproc_of_match

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

This relocation avoids the need to declare function prototypes such as
'static int imx_rproc_xtr_mbox_init(struct rproc *rproc, bool tx_block)'
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>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Link: https://lore.kernel.org/r/20250910-imx-rproc-cleanup-v2-2-10386685b8a9@nxp.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>