drm/bridge: ti-sn65dsi86: Set max register for regmap

Set the maximum register to 0xff so we can dump the registers for this
device in debugfs.

Fixes: a095f15c ("drm/bridge: add support for sn65dsi86 bridge driver")
Cc: Rob Clark <robdclark@chromium.org>
Cc: Douglas Anderson <dianders@chromium.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20211215002529.382383-1-swboyd@chromium.org

drivers/gpu/drm/bridge/ti-sn65dsi86.c

@@ -213,6 +213,7 @@ static const struct regmap_config ti_sn65dsi86_regmap_config = {
 	.val_bits = 8,
 	.volatile_table = &ti_sn_bridge_volatile_table,
 	.cache_type = REGCACHE_NONE,
+	.max_register = 0xFF,
 };
 
 static int __maybe_unused ti_sn65dsi86_read_u16(struct ti_sn65dsi86 *pdata,