Exclude altivec code paths if the compiler does not support them

kernel/power/drot.c

@@ -40,8 +40,10 @@ USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #pragma GCC optimize "O1"
 
 #if defined(POWER8) || defined(POWER9) || defined(POWER10)
+#if defined(__VEC__) || defined(__ALTIVEC__)
 #include "drot_microk_power8.c"
 #endif
+#endif
 
 
 #ifndef HAVE_KERNEL_16