drm/loongson: Add a check for lsdc_bo_create() errors

This code doesn't check for lsdc_bo_create() failure and it could lead
to a crash.  It can fail for a variety of reasons, but the most common
cause would be low memory.  Add a check.

Fixes: f39db26c

 ("drm: Add kms driver for loongson display controller")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Sui Jingfeng <suijingfeng@loongson.cn>
Signed-off-by: Sui Jingfeng <sui.jingfeng@linux.dev>
Link: https://patchwork.freedesktop.org/patch/msgid/ZLeijglIMPve2Iio@kadam