All identifiers, regardless of use, that start with two underscores are
reserved. This means they can't be used in header guards.

The style that this project is now to use the full name of the file in
capital letters followed by 'H'. For example, for a file called
"uart_example.h", the header guard is UART_EXAMPLE_H.

The exceptions are files that are imported from other projects:

- CryptoCell driver
- dt-bindings folders
- zlib headers

Change-Id: I50561bf6c88b491ec440d0c8385c74650f3c106e
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Boot memory layout is specific for a platform, but should not be
mixed up with other platform specific attributes. A separate file is
much cleaner and better to compare with other platforms. Take a look
at plat/poplar where it is done the same way.

Moved hikey_def.h to system include folder and moved includes from
hikey_def.h to more general platform_def.h.

Signed-off-by: Michael Brandl <git@fineon.pw>