remoteproc: imx_rproc: Move common structure to header file

Move common structure imx_rproc_att, imx_rproc_method
and imx_rproc_dcfg to header file which can be shared with
imx_dsp_rproc driver.

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Link: https://lore.kernel.org/r/1633944015-789-2-git-send-email-shengjiu.wang@nxp.com


Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>