soc: qcom: pil: allow subsystem to allocate extra memory

Allow the subsystem to use some extra memory allocated
after the end of the image, for the subsystem to use.

This is porting from Kona of commit SHA:1279fb070282.

Change-Id: I79d19c9e48b7893d10ac814fb42e5783651417b4
Signed-off-by: Nurit Lichtenstein <nuritl@codeaurora.org>