SPM: Shorten names of types and functions

The current internal names are too long, which makes it hard to write
code as many lines overflow the limit and need to be split, which may
not help the reader.

Change-Id: I072bdc8f3dd125255063ffa7f02500e5228fc9a1
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>