ANDROID: GKI: drivers: of: Add APIs to find DDR device rank, HBB

Add APIs to find the DDR device rank and Highest
Bank Bit (HBB) information from their respective
memory nodes.

Bug: 153905290
Test: compile
Change-Id: Iae94efc681daf2cf0a531dceb8d2acdcf3484388
Signed-off-by: Kaushal Kumar <kaushalk@codeaurora.org>
(cherry picked from commit 789ad9a7a829c6c423125eac3490967916c46ba9)
Signed-off-by: Will McVicker <willmcvicker@google.com>