meson: split udev from udev_kms which requires systemd

DragonFly and FreeBSD can use xf86-input-libinput with config/udev.

ld: error: undefined symbol: xf86PlatformDeviceProbe
>>> referenced by xf86platformBus.c
>>>               xf86platformBus.c.o:(xf86platformProbe) in archive hw/xfree86/common/libxorg_common.a

ld: error: undefined symbol: xf86PlatformDeviceCheckBusID
>>> referenced by xf86platformBus.c
>>>               xf86platformBus.c.o:(xf86platformProbeDev) in archive hw/xfree86/common/libxorg_common.a

ld: error: undefined symbol: xf86PlatformReprobeDevice
>>> referenced by xf86platformBus.c
>>>               xf86platformBus.c.o:(xf86platformVTProbe) in archive hw/xfree86/common/libxorg_common.a

ld: error: undefined symbol: NewGPUDeviceRequest
>>> referenced by udev.c
>>>               udev.c.o:(device_added) in archive config/liblibxserver_config.a

ld: error: undefined symbol: DeleteGPUDeviceRequest
>>> referenced by udev.c
>>>               udev.c.o:(device_removed) in archive config/liblibxserver_config.a
4 jobs for freebsd in 5 minutes and 11 seconds (queued for 1 second)