Trivial fix to spelling mistake in DRM_ERROR error message
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180502101048.8442-1-colin.king@canonical.com