compositor-openwfd: Use wfd_device_id as drm fd
compositor-openwfd: Use wfd_device_id as drm fd

owfdrm uses non-0 (0 == WFD_INVALID_DEVICE_ID) fd's as wfd_device_ids.
This is not standardized, but also not invalid.

Tarnyko/weston-xdg_surface_present,krezovic/weston,Tarnyko/weston-xdg_surface_present,Gnurou/weston,giucam/weston,mchalupa/weston,kwm81/weston,jonnylamb/weston,udoprog/weston,eyolfson/weston,sir-murray/weston,kwm81/weston,Gnurou/weston,xorgy/weston,giucam/weston,Fantu/compositor-spice,krezovic/weston,jonnylamb/weston,sir-murray/weston,Fantu/compositor-spice,Fantu/compositor-spice,eyolfson/weston,mchalupa/weston,xorgy/weston,udoprog/weston