gen_corev-dv makefile target cleanup

Created by: silabs-hfegran

Simplified gen_corev-dv makefile target as follows:

• Removed superfluous clean old tests-section (rsync will fail if output files are missing, and will properly overwrite files in the destination directory anyway)

• replaced cp with rsync, to enable cleanup of output folder after completion (This will ensure that only newly generated files are copied to the test location)

• Comment removed to enable && \ after xrun-command and avoid the no-op ls-command (Comments do not play well inside split lines)

Signed-off-by: Henrik Fegran Henrik.Fegran@silabs.com