drm/vc4: dsi: Use snprintf for the PHY clocks instead of an array

drm/vc4: dsi: Use snprintf for the PHY clocks instead of an array

[ Upstream commit dc0bf36401e891c853e0a25baeb4e0b4e6f3626d ]

The DSI clocks setup function has been using an array to store the clock
name of either the DSI0 or DSI1 blocks, using the port ID to choose the
proper one.

Let's switch to an snprintf call to do the same thing and simplify the
array a bit.

Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20201203132543.861591-4-maxime@cerno.tech
Signed-off-by: Sasha Levin <sashal@kernel.org>