driver core: Clarify that dev_err_probe() is OK even w/out -EPROBE_DEFER

There is some debate about whether it's deemed acceptable to call
dev_err_probe() if you know that the error code can never be
-EPROBE_DEFER. Clarify in the function comments that this is
OK. Specifically this makes us able to transform code like this:

  ret = do_something_that_cant_defer();
  if (ret < 0) {
    dev_err(dev, "The foo failed to bar (%pe)\n", ERR_PTR(ret));
    return ret;
  }

to code like this:
  ret = do_something_that_cant_defer();
  if (ret < 0)
    return dev_err_probe(dev, ret, "The foo failed to bar\n");

It is also possible that in the future folks might want a CONFIG
option to strip out all probe error strings to save space (keeping
non-probe errors) with the argument that probe errors rarely happen
after bringup. Having probe errors reported with a consistent function
would allow that.

Cc: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20210916161931.1.I32bea713bd6c6fb419a24da73686145742b6c117@changeid
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/core.c

@@ -4653,6 +4653,11 @@ define_dev_printk_level(_dev_info, KERN_INFO);
  *
  * 	return dev_err_probe(dev, err, ...);
  *
+ * Note that it is deemed acceptable to use this function for error
+ * prints during probe even if the @err is known to never be -EPROBE_DEFER.
+ * The benefit compared to a normal dev_err() is the standardized format
+ * of the error code and the fact that the error code is returned.
+ *
  * Returns @err.
  *
  */