asus_atk0110: Use non-deprecated registration and managed memory

[Bastian Germann]

This is version 4 of my previously unversioned patch.

Version 2 addresses the issues brought up by Guenter.
The two v1 patches are joined in v2 1/2.
The unnecessary dynamic allocations are now part of the atk_data struct.
devm_kcalloc is used for the attribute array that is created from sensors.
v2 2/2 replaces all dynamic allocations in the driver with the device
managed devm_* versions. All corresponding kfree calls are removed.

Version 3 addresses the issue brought up by Andy.
v3 1/2 is unchanged. v3 2/2 reverses one of the devm_kzalloc changes of v2
because it introduces a memory leak.

v4 1/2 changes the attr_group field to only contain one item.
v4 2/2 is unchanged.