drm/bridge: ite-it6263: Prevent error pointer dereference in probe()

If devm_i2c_new_dummy_device() fails then we were supposed to return an
error code, but instead the function continues and will crash on the next
line.  Add the missing return statement.

Fixes: 04972362 ("drm/bridge: Add ITE IT6263 LVDS to HDMI converter")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Liu Ying <victor.liu@nxp.com>
Signed-off-by: Liu Ying <victor.liu@nxp.com>
Link: https://patchwork.freedesktop.org/patch/msgid/804a758b-f2e7-4116-b72d-29bc8905beed@stanley.mountain