soc: qcom: smem: Support global partition

SMEM V12 creates a global partition to allocate global
smem items from instead of a global heap. The global
partition has the same structure as a private partition.

Change-Id: I5ed5206e7f89665cac3eb93fdd93796078dbd521
Signed-off-by: Chris Lew <clew@codeaurora.org>