kernel/ksysfs.c: use helper macro __ATTR_RW

Use helper macro __ATTR_RW to define kobj_attribute to make code more
clear.  Minor readability improvement.

Link: https://lkml.kernel.org/r/20220222112034.48298-1-linmiaohe@huawei.com


Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>