sh: kdump: add some attribute to function

add '__iomem' for ioremap() and '__user' for copy_to_user().

Signed-off-by: Yejune Deng <yejune.deng@gmail.com>
Tested-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Signed-off-by: Rich Felker <dalias@libc.org>