juno: Rework header file inclusion ...

Change-Id: I0837d787837a40a724a8b7f2e3abd82287f403f3

juno: Fix build errors due to recent changes ...

This is a miscellaneous commit that fixes all build
errors introduced by the rebase of the Juno codebase
on the latest trusted firmware.

 - Make codebase consistent in its use of #include "" syntax
   for user includes and #include <> syntax for system includes.

 - Sort header files alphabetically

 - Use tag names for structure types.
   Replace instances of the former io_handle and io_dev_handle
   types with uintptr_t.

 - Review the .c and .S files for which header files really need
   including and reorder the #include statements alphabetically.

Change-Id: I1d409fafb6dc257a38992ee15b22b0e890d040b0

juno: Add MHU interface ...

Signed-off-by: Jon Medhurst <tixy@linaro.org>