port reduced version of remoteproc framework from linux ...

I tested it on phytec imx7 board with remoteproc ELF image previously used on
Linux. Linux would load this image, create appropriate resource (if defined in
image) and boot it. The barebox version is only loading image and boot it.

Currently barebox version do not extract resources defined by rproc ELF image.
On this early stage it is hard to say, if it is needed.

Previously there was an attempt to port bootaux command from u-boot.
Porting of remoteproc framework is my attempt to lead this topic in to the
(IMO) right direction.

To start remoteproc image, firmwareload command should be used:
firmwareload /mnt/tftp/rproc-imx-rproc-fw

Since firmwareload already support multiple targets, it is possible to
specify which exact cortex m4 CPU should be started (if multiple CPU are
present). This example shows the list of available firmware targets:
barebox@Phytec i.MX7 phyBOARD-Zeta:/ firmwareload -l
firmware programming handlers:

name:      model:
soc:imx7d-rp0@0.of

Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>