driver core: fix documentation of request_firmware_nowait

request_firmware_nowait declares it can be called in non-sleep contexts,
but kthead_run called by request_firmware_nowait may sleep. So fix its
documentation and comment to make callers clear about it.
Signed-off-by: NMing Lei <tom.leiming@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Documentation/firmware_class/README

@@ -77,7 +77,8 @@
    seconds for the whole load operation.
 
  - request_firmware_nowait() is also provided for convenience in
-   non-user contexts.
+   user contexts to request firmware asynchronously, but can't be called
+   in atomic contexts.
 
 
  about in-kernel persistence:

drivers/base/firmware_class.c

@@ -617,8 +617,9 @@ request_firmware_work_func(void *arg)
  * @cont: function will be called asynchronously when the firmware
  *	request is over.
  *
- *	Asynchronous variant of request_firmware() for contexts where
- *	it is not possible to sleep.
+ *	Asynchronous variant of request_firmware() for user contexts where
+ *	it is not possible to sleep for long time. It can't be called
+ *	in atomic contexts.
  **/
 int
 request_firmware_nowait(