uboot-phytec

i2c: designware_i2c: Use an enum for selected speed mode

Group these #defines into an enum to make it easier to understand the
relationship between them.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jun Chen <ptchentw@gmail.com>
Reviewed-by: Heiko Schocher <hs@denx.de>