Standardise header guards across codebase ...

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>

plat/arm: Move norflash driver to drivers/ folder ...

This way it can be reused by other platforms if needed.

Note that this driver is designed to work with the Versatile Express NOR
flash of Juno and FVP. In said platforms, the memory is organized as an
interleaved memory of two chips with a 16 bit word.

Any platform that wishes to reuse it with a different configuration will
need to modify the driver so that it is more generic.

Change-Id: Ic721758425864e0cf42b7b9b04bf0d9513b6022e
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>