SPM: Combine PSP and PSPLIM set opeartion into one function

PSP and PSPLIM (Or the virtual PSPLIM for earlier architectures)
was set respectively by calling two functions, even though the
set operations are always paired.

Create a dedicated function for setting process stacks and apply
PSP and PSPLIM setting this function.

Signed-off-by: Ken Liu <Ken.Liu@arm.com>
Change-Id: I8161256eedfaf2cd025770fb2e7096947571ef0a
4 files changed