Sam James authored Dec 07, 2021 and Povilas Kanapickas committed Dec 14, 2021

Initially reported downstream in Gentoo. Manifests with errors like:
```
gnu/bin/ld: hw/xfree86/common/libxorg_common.a(xf86fbBus.c.o): in function `xf86ClaimFbSlot':
xf86fbBus.c:(.text+0x20): undefined reference to `sbusSlotClaimed'
/usr/lib/gcc/sparc-unknown-linux-gnu/11.2.0/../../../../sparc-unknown-linux-gnu/bin/ld: xf86fbBus.c:(.text+0x2c): undefined reference to `sbusSlotClaimed'
```

While we use the headers in meson.build, we don't reference xf86sbusBus.c
which defines the missing symbols like sbusSlotClaimed.

Bug: https://bugs.gentoo.org/828513


Signed-off-by: Sam James <sam@gentoo.org>