dmadev: add channel status check for testing use

dmadev: add channel status check for testing use

Add in a function to check if a device or vchan has completed all jobs
assigned to it, without gathering in the results. This is primarily for
use in testing, to allow the hardware to be in a known-state prior to
gathering completions.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Reviewed-by: Conor Walsh <conor.walsh@intel.com>
Reviewed-by: Kevin Laatz <kevin.laatz@intel.com>