remoteproc: imx_dsp_rproc: Add custom memory copy implementation for i.MX DSP Cores

In the Linux kernel, the following vulnerability has been resolved:

remoteproc: imx_dsp_rproc: Add custom memory copy implementation for i.MX DSP Cores

The IRAM is part of the HiFi DSP. According to hardware specification only 32-bits write are allowed otherwise we get a Kernel panic.

Therefore add a custom memory copy and memset functions to deal with the above restriction.