Documentation: dmaengine: Correctly describe dmatest with channel unset

Currently the documentation states that channels must be configured before
running the dmatest. This has not been true since commit 6b41030f
("dmaengine: dmatest: Restore default for channel"). Fix accordingly.

Fixes: 6b41030f ("dmaengine: dmatest: Restore default for channel")
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20211118100952.27268-3-daniel.thompson@linaro.orgSigned-off-by: Vinod Koul <vkoul@kernel.org>

Documentation/driver-api/dmaengine/dmatest.rst

@@ -153,13 +153,14 @@ Part 5 - Handling channel allocation
 Allocating Channels
 -------------------
 
-Channels are required to be configured prior to starting the test run.
-Attempting to run the test without configuring the channels will fail.
+Channels do not need to be configured prior to starting a test run. Attempting
+to run the test without configuring the channels will result in testing any
+channels that are available.
 
 Example::
 
     % echo 1 > /sys/module/dmatest/parameters/run
-    dmatest: Could not start test, no channels configured
+    dmatest: No channels configured, continue with any
 
 Channels are registered using the "channel" parameter. Channels can be requested by their
 name, once requested, the channel is registered and a pending thread is added to the test list.