drm: fix free illegal pointer when create drm_property_blob failed

euler inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8RJA9?from=project-issue


CVE: NA

---------------------------

we get (Unable to handle kernel NULL pointer dereference at virtual
address 000000000000000c) when call drm_property_blob_put().
After analysis, we get the following process:
alloc failed:
drm_atomic_set_mode_for_crtc()
    drm_property_create_blob() // failed
    state->mode_blob = ERR_PTR(-ENOMEM)
free illegal pointer:
__drm_atomic_helper_crtc_destroy_state()
    drm_property_blob_put(state->mode_blob)
	    drm_mode_object_put(&blob->base);   // here blob is ERR_PTR(-ENOMEM)
So do we have to determine if blob is an error code
before calling drm_mode_object_put().

Fixes: 6bcacf51 (drm: Add reference counting to blob properties)
Signed-off-by: zhangnaichuan <zhangnaichuan@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>