backlight: Switch i2c drivers back to use .probe()

After commit b8a1a4cd ("i2c: Provide a temporary .probe_new()
call-back type"), all drivers being converted to .probe_new() and then
03c835f4 ("i2c: Switch .probe() to not take an id parameter") convert
back to (the new) .probe() to be able to eventually drop .probe_new() from
struct i2c_driver.

Also fix two indention inconsistencies in the neighbourhood.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20230521143844.375244-1-u.kleine-koenig@pengutronix.de


Signed-off-by: Lee Jones <lee@kernel.org>