slim_ngd: Slimbus satellite controller driver

NGD (non-ported generic device, also known as satellite device) is
used to implement light-weight slimbus controller driver.
This driver is responsible for:
1. Communicating with codec (or any slimbus slave registered from
application processor side) directly using slimbus HW messaging
interface.
2. Communicating with the manager device (controller by master driver)
on LPASS to do bandwidth and data channel management. NGD takes these
requests from slimbus slave on application processor side and passes
them to the manager device using slimbus messaging itself.
SPS BAM is used for receiving messages to offload CPU, and to enable
receiving multiple messages before driver can process them.
Runtime-pm is used for power management. Controller is in active
power state when messaging and/or data-channels are active from
application processor side.

Change-Id: Iff53c0ca9b768a3dac3bccb5004fd2f96070af50
Signed-off-by: Sagar Dharia <sdharia@codeaurora.org>