soc: qualcomm: Add Shared Memory Manager driver

soc: qualcomm: Add Shared Memory Manager driver

The Shared Memory Manager driver implements an interface for allocating
and accessing items in the memory area shared among all of the
processors in a Qualcomm platform.

Adapted from the Linux driver (4.17)

Changes from the original Linux driver:
* Removed HW spinlock mechanism, which is irrelevant
in U-boot particualar use case, which is just reading from the smem.
* Adapted from Linux driver model to U-Boot's.

Cc: Bjorn Andersson <[email protected]>
Signed-off-by: Ramon Fried <[email protected]>
Reviewed-by: Simon Glass <[email protected]>