gpu: host1x: Disable clock on probe failure

Add a missing clk_disable_unprepare() before returning from the driver's
.probe() function on error.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>