drm/bridge: migrate bridge_chains to per-encoder file

Instead of having a single file with all bridge chains, list bridges
under a corresponding per-encoder debugfs directory.

While we are at it, also slightly improve the formatting of the bridge
data: split a single line entry into multiple lines, include the symbol
name of the bridge funcs and add the textual representation of the
bridge ops.

Example of the listing:

$ cat /sys/kernel/debug/dri/0/encoder-0/bridges
bridge[0]: dsi_mgr_bridge_funcs
	type: [0] Unknown
	ops: [0]
bridge[1]: lt9611uxc_bridge_funcs
	type: [11] HDMI-A
	OF: /soc@0/geniqup@9c0000/i2c@994000/hdmi-bridge@2b:lontium,lt9611uxc
	ops: [7] detect edid hpd

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20231203115315.1306124-3-dmitry.baryshkov@linaro.org