drm/bridge: lt8912b: fix corrupted image output

Correct I2C address for the register list in lt8912_write_lvds_config(),
these registers are on the first I2C address (0x48), the current
function is just writing garbage to the wrong registers and this creates
multiple issues (artifacts and output completely corrupted) on some HDMI
displays.

Correct I2C address comes from Lontium documentation and it is the one
used on other out-of-tree LT8912B drivers [1].

[1] https://github.com/boundarydevices/linux/blob/boundary-imx_5.10.x_2.0.0/drivers/video/lt8912.c#L296

Fixes: 30e2ae94 ("drm/bridge: Introduce LT8912B DSI to HDMI bridge")
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Signed-off-by: Philippe Schenker <philippe.schenker@toradex.com>
Acked-by: Adrien Grassein <adrien.grassein@gmail.com>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220922124306.34729-4-dev@pschenker.ch
Link: https://patchwork.freedesktop.org/patch/msgid/20220922124306.34729-5-dev@pschenker.ch

drivers/gpu/drm/bridge/lontium-lt8912b.c

@@ -196,7 +196,7 @@ static int lt8912_write_lvds_config(struct lt8912 *lt)
 		{0x03, 0xff},
 	};
 
-	return regmap_multi_reg_write(lt->regmap[I2C_CEC_DSI], seq, ARRAY_SIZE(seq));
+	return regmap_multi_reg_write(lt->regmap[I2C_MAIN], seq, ARRAY_SIZE(seq));
 };
 
 static inline struct lt8912 *bridge_to_lt8912(struct drm_bridge *b)