dt-bindings: msm: dsi: Add missing clocks to 28nm DSI PHY YAML

Add in missing clock and clock-names declarations to the 28nm DSI PHY.
When converting from .txt to .yaml we missed these.

Fixes: 4dbe55c9 ("dt-bindings: msm: dsi: add yaml schemas for DSI bindings")
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>