remoteproc: imx_dsp_rproc: Fix kernel test robot sparse warning

[ Upstream commit 3c497f62 ]

This patch fixes the kernel test robot warning reported here:

https://lore.kernel.org/bpf/642f916b.pPIKZ%2Fl%2F%2Fbw8tvIH%25lkp@intel.com/T/

Fixes: 408ec1ff

 ("remoteproc: imx_dsp_rproc: Add custom memory copy implementation for i.MX DSP Cores")
Link: https://lore.kernel.org/r/20230407161429.3973177-1-mathieu.poirier@linaro.org
Tested-by: Iuliana Prodan <iuliana.prodan@nxp.com>
Reviewed-by: Iuliana Prodan <iuliana.prodan@nxp.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>