On systems that have multiple platform components that can interpret the
SCMI messages, there is a need to support multiple SCMI channels (one
each to those platform components). Extend the existing SCMI interface
that currently supports only a single SCMI channel to support multiple
SCMI channels.

Change-Id: Ice4062475b903aef3b5e5bc37df364c9778a62c5
Signed-off-by: Aditya Angadi <aditya.angadi@arm.com>

Improved support for W=1 compilation flag by solving missing-prototypes
and old-style-definition warnings.

The libraries are compiling with warnings (which turn into errors with
the Werror flag).

Outside of libraries, some warnings cannot be fixed without heavy
structural changes.

Change-Id: I1668cf99123ac4195c2a6a1d48945f7a64c67f16
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>

Change-Id: I8989d2aa0258bf3b50a856c5b81532d578600124
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>