nvmem: Add snapshot of QTI SDAM driver

QTI SDAM driver allows PMIC peripherals to access the shared
memory that is available on QTI PMICs. Add device tree bindings
documentation for it.

This snapshot is taken as of msm-4.14
commit 9bb584ae ("msm/sde/rotator: Add rev checks for sdmmagpie").

Change-Id: If83c87a9e162b442b362f1b3af619d481514f7bf
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>