Fix build on FreeBSD/powerpc*

Current error:
ld: error: undefined symbol: xf86EnableIO
>>> referenced by xf86Configure.c
>>>               libxorg_common.a.p/xf86Configure.c.o:(DoConfigure) in archive hw/xfree86/common/libxorg_common.a
>>> referenced by xf86Events.c
>>>               libxorg_common.a.p/xf86Events.c.o:(xf86VTEnter) in archive hw/xfree86/common/libxorg_common.a
>>> referenced by xf86Init.c
>>>               libxorg_common.a.p/xf86Init.c.o:(InitOutput) in archive hw/xfree86/common/libxorg_common.a
>>> referenced 1 more times