[PATCH] docs: dmaengine: add explanation for DMA_ASYNC_TX capability

[kendrajmoore <kendra.j.moore3443@gmail.com>]

From: Kendra Moore <kendra.j.moore3443@gmail.com>

This patch replaces the TODO for DMA_ASYNC_TX in the DMA engine
provider documentation. The flag is automatically set by the DMA
framework when a device supports key asynchronous memory-to-memory
operations such as memcpy, memset, xor, pq, xor_val, and pq_val.

It must not be set by drivers directly.

Signed-off-by: Kendra Moore <kendra.j.moore3443@gmail.com>
---
 Documentation/driver-api/dmaengine/provider.rst | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/Documentation/driver-api/dmaengine/provider.rst b/Documentation/driver-api/dmaengine/provider.rst
index 3085f8b460fa..aac2a18bd453 100644
--- a/Documentation/driver-api/dmaengine/provider.rst
+++ b/Documentation/driver-api/dmaengine/provider.rst
@@ -217,10 +217,12 @@ Currently, the types available are:
 
 - DMA_ASYNC_TX
 
-  - Must not be set by the device, and will be set by the framework
-    if needed
+  - The device supports asynchronous memory-to-memory operations,
+    including memcpy, memset, xor, pq, xor_val, and pq_val.
 
-  - TODO: What is it about?
+  - This capability is automatically set by the DMA engine
+    framework and must not be configured manually by device
+    drivers.
 
 - DMA_SLAVE
 
-- 
2.39.5