dt-bindings: msm: dsi-controller-main: Fix clock declarations

When converting from .txt to .yaml dt-binding descriptions we appear to
have missed some of the previous detail on the number and names of
permissible clocks.

Fix this by listing the clock descriptions against the clock names at a
high level.

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