drm: Add missing field copy in compat_drm_version

DRM_IOCTL_VERSION is supposed to update the name_len/date_len/desc_len
fields to user.

Fixes: 012c6741 ("switch compat_drm_version() to drm_ioctl_kernel()")
Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>