drm: fix drm_mode_create_blob comment

Just a silly mistake

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Suggested-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Simon Ser <contact@emersion.fr>
Signed-off-by: Simon Ser <contact@emersion.fr>
Link: https://patchwork.freedesktop.org/patch/msgid/20210302184427.1301264-1-lionel.g.landwerlin@intel.com