bus: mvebu-mbus: use DEFINE_SHOW_ATTRIBUTE to simplify mvebu_{sdram/devs}_debug

Use DEFINE_SHOW_ATTRIBUTE helper macro to simplify the code.

Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Link: https://lore.kernel.org/r/20220916141244.2174005-1-liushixin2@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>