staging: vchiq: Unify fourcc definition mechanisms

There is already enough duplication with regard to fourcc generation in
the kernel. Let's at least use the same macro all over the vchiq
ecosystem.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Link: https://lore.kernel.org/r/20200629150945.10720-35-nsaenzjulienne@suse.de


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>