wayland: Drop support for linux dmabuf buffer flags

A client can specify the following flags when creating a linux dmabuf
client buffer:

- y_invert
- interlaced
- bottom_first

Only the y_invert flag is supported by kwin. The interlaced and the
bottom_first flags are ignored. On the other hand, most clients don't
specify the dmabuf flags. For example, neither EGL nor Vulkan WSIs
use the y_invert flag.

The y_invert flag is undesired because it also blocks optimizations such
as direct scanout because DRM assumes that the origin is in the top left
corner.

Therefore, this change drops the support for linux dmabuf flags. From
the protocol perspective, this is fine. It can be viewed as buffer
import failing with the specified flags.