sh: checksum: add missing linux/uaccess.h include

SuperH does not include uaccess.h, even tho it calls access_ok().

Fixes: 68f4eae7

 ("net: checksum: drop the linux/uaccess.h include")
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Tested-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20230128073108.1603095-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>