remoteproc: imx_rproc: Change to ioremap_wc for dram

remoteproc: imx_rproc: Change to ioremap_wc for dram

DRAM is not io memory, so changed to ioremap_wc. This is also
aligned with core io accessories. e.g. memcpy/memset and cpu direct
access.

Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Peng Fan <peng.fan@nxp.com>
Reviewed-and-tested-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Link: https://lore.kernel.org/r/20210910090621.3073540-7-peng.fan@oss.nxp.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>