And add ifndef guards for cases were do have support for it.

While at it I need to change how we build it due to:

'meson.build:21:0: ERROR: Value "false" (of type "string") for combo
option "Enable support for vc4's KMS API." is not one of the choices.
Possible choices are (as string): "enabled", "disabled", "auto".'

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>