drm: Allow creating blob properties without copy
drm: Allow creating blob properties without copy

Make the data parameter to drm_property_create_blob optional; if
omitted, the copy will be skipped and the data will be empty.

Signed-off-by: Daniel Stone <62e7e355d5d8400fa8384448796af0bf6be4ffae@collabora.com>
Reviewed-by: Maarten Lankhorst <743c2818a341d71b99ed2b566f9f80c2fc288f93@intel.com>
Tested-by: Sean Paul <f9352ecf3e2294bdb914c99cca8d12601acec118@chromium.org>
Signed-off-by: Daniel Vetter <c1b6782c4af8f0673da8923a0702a1832e5940f4@ffwll.ch>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs