apps: linux: generic: Use accessor functions for struct remoteproc_mem

[glneo]

The remoteproc_mem struct contents are internal to remoteproc. The struct should be accessed using the provided accessors, not directly. This is done in preperation of making this struct opaque to code outside of the remoteproc drivers.

[glneo]

do you plan to propose anupdate for other application that also abuse of the remoteproc_mem struct?

Yes, here let me add a couple more to this series.

[arnopo]

@tanmays, @bentheredonethat Is it ok for you?

[bentheredonethat]

yes LGTM