drivers/base/memory.c: Use DEVICE_ATTR_RO and friends

Let's use the easier to read (and not mess up) variants:
- Use DEVICE_ATTR_RO
- Use DEVICE_ATTR_WO
- Use DEVICE_ATTR_RW
instead of the more generic DEVICE_ATTR() we're using right now.

We have to rename most callback functions. By fixing the intendations we
can even save some LOCs.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: Oscar Salvador <osalvador@suse.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>