In multiRU we will need to be able to check multiple devices and DMA channels, not only /dev/sdr0@0 that was implicitly used until now.

-> As a preparatory step adjust the SR to explicitly specify which SDR resource is being verified.

This patch is necessary because in slapos.toolbox!125 (merged) we adjust check_sdr_busy plugin to require SDR device/DMA channel to be explicitly specified.

/cc @jhuge, @lu.xu, @tomo, @xavier_thompson, @Daetalus