EISA: use DEVICE_ATTR_RO() helper macro

Use DEVICE_ATTR_RO() helper macro instead of DEVICE_ATTR(), which makes
the code a bit shorter and easier to read.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Link: https://lore.kernel.org/r/20210603090506.11771-1-thunder.leizhen@huawei.com


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