soc: qcom: mem-offline: Set offlinable region based on minimum DDR sizes

Currently we use a percentage property value to determine the amount of
offlinable memory in the system.

However a percentage property doesn't support accurately configuring the
offlinable region sizes on targets with different amounts of DDR.
For example it is not possible to configure the system such that 4GB
targets won't have any offlinable region, 6GB targets will have a 1GB
offlinable region and 8GB targets having a 3GB offlinable region without
creating a separate DT files for each target.
Many customers want to be able to support different DDR sizes without
creating separate DT files for each target.

Replace the  mem-percent property with an offline-sizes property which
contains an array of offlinable memory region sizes to apply to targets
based on their DDR size.

Change-Id: I93210beec153ca0179c0087ce98afd4dfc22ea02
Signed-off-by: Liam Mark <lmark@codeaurora.org>