SPA_MEMBER is misleading, all we're doing here is pointer+offset and a
type-casting the result. Rename to SPA_PTROFF which is more expressive (and
has the same number of characters so we don't need to re-indent).
libcamera is depending on libdrm in libcamera_wrapper.cpp but it was
implicitely including the header drm_fourcc.h with libcamera
file pixel_format.h
With this patch, the libcamera plugin should explicitely depends on
libdrm as it needs DRM fourcc and should not depend on multiple
inclusion from libcamera.
Add a FourCC for Motion-JPEG compressed format. This is a temporary
addition until the format gets merged in the upstream kernel.
