power: add SMB1390 charge pump driver

SMB1390 is a charge pump PMIC and is used as a companion charger to the
primary charging PMIC. This driver implements all of the required
functionality to be used as a parallel charger.

This is a snapshot of commit "power: add SMB1390 charge pump driver" in
kernel 4.9, with two modifications:

- cp_class_attrs -> cp_class_groups. This change was necessitated by
  'commit ced6473e ("driver core: class: add class_groups support")'
  and 'commit ecbaa83e ("driver core: remove class_attrs from
  struct class")'.

- Use the IIO framework to read die temperature instead of the older
  qpnp-vadc framework. Also, add an INFO message to signify successful
  probing of driver.

CRs-Fixed: 2200333
Change-Id: I9e58773241a2b9865067ac563ca96a75afc34611
Signed-off-by: Nicholas Troast <ntroast@codeaurora.org>
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>
Signed-off-by: Umang Agrawal <uagrawal@codeaurora.org>
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>