drm/bridge: adv7511/33: Fix adv7511_cec_init() failure handling

If the device tree for a board did not specify a cec clock, then
adv7511_cec_init would return an error, which would cause adv7511_probe()
to fail and thus there is no HDMI output.

There is no need to have adv7511_probe() fail if the CEC initialization
fails, so just change adv7511_cec_init() to a void function. In addition,
adv7511_cec_init() should just return silently if the cec clock isn't
found and show a message for any other errors.

An otherwise correct cleanup patch from Dan Carpenter turned this broken
failure handling into a kernel Oops, so bisection points to commit
7af35b0a ("drm/kirin: Checking for IS_ERR() instead of NULL") rather
than 3b1b9750

 ("drm: adv7511/33: add HDMI CEC support").

Based on earlier patches from Arnd and John.

Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Cc: Xinliang Liu <xinliang.liu@linaro.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Sean Paul <seanpaul@chromium.org>
Cc: Archit Taneja <architt@codeaurora.org>
Cc: John Stultz <john.stultz@linaro.org>
Link: https://bugs.linaro.org/show_bug.cgi?id=3345
Link: https://lkft.validation.linaro.org/scheduler/job/48017#L3551
Fixes: 7af35b0a ("drm/kirin: Checking for IS_ERR() instead of NULL")
Fixes: 3b1b9750

 ("drm: adv7511/33: add HDMI CEC support")
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Tested-by: Hans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: https://patchwork.freedesktop.org/patch/msgid/9097b2a4-b6b9-5fca-e039-0a17694b1143@xs4all.nl