Enforce full include path for includes. Deprecate old paths.

The following folders inside include/lib have been left unchanged:

- include/lib/cpus/${ARCH}
- include/lib/el3_runtime/${ARCH}

The reason for this change is that having a global namespace for
includes isn't a good idea. It defeats one of the advantages of having
folders and it introduces problems that are sometimes subtle (because
you may not know the header you are actually including if there are two
of them).

For example, this patch had to be created because two headers were
called the same way: e0ea0928d5b7 ("Fix gpio includes of mt8173 platform
to avoid collision."). More recently, this patch has had similar
problems: 46f9b2c3a282 ("drivers: add tzc380 support").

This problem was introduced in commit 4ecca33988b9 ("Move include and
source files to logical locations"). At that time, there weren't too
many headers so it wasn't a real issue. However, time has shown that
this creates problems.

Platforms that want to preserve the way they include headers may add the
removed paths to PLAT_INCLUDES, but this is discouraged.

Change-Id: I39dc53ed98f9e297a5966e723d1936d6ccf2fc8f
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

The current SPM is a prototype that only supports one secure partition
in EL0. The objective of SPM is to have multiple partitions. The current
MM interface isn't adequate for this, so it is needed to modify heavily
the code to add proper support for it.

However, there are platforms which are already using this (like SGI) and
removing the code would break it.  For this reason, the current SPM code
has been duplicated in order to temporarily preserve compatibility. All
new improvements/changes to SPM will be done in the non-deprecated copy,
that may change without notice.

The new build option SPM_DEPRECATED has been introduced to select the SPM
implementation. It defaults to 1, that selects the deprecated SPM.

Change-Id: Ic9f80b53b450e97b4d3f47e4ef4a138ee8d87443
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>