[U-Boot] [PATCH v2 1/3] dm: core: Clarify uclass_first/next_device() comments

[sjg at google.com]

These are not as clear as they could be. Tidy them up a bit. Also fix a
tiny code-style nit.

Signed-off-by: Simon Glass <sjg at chromium.org>
---

Changes in v2: None

 drivers/core/uclass.c |  3 +--
 include/dm/uclass.h   | 13 +++++++++++--
 2 files changed, 12 insertions(+), 4 deletions(-)

Applied to u-boot-dm, thanks!