math/sleef: fix build on powerpc64le

ld: error: duplicate symbol: sleef_cpuidtmp2

defined at dispscalar.c

src/libm/CMakeFiles/dispscalar_obj.dir/dispscalar.c.o:(sleef_cpuidtmp2)

defined at tryvsx3.c

src/libm/CMakeFiles/tryvsx3_obj.dir/tryvsx3.c.o:(.bss+0x10)