sgemm_direct_skylakex: fix 75eeb26 regression.

The
`#if defined(SKYLAKEX) || defined (COOPERLAKE)`
from that commit was before #include "common.h" so caused the
compiled function to be empty, returning garbage results for
qualifying sgemm's on those architectures.

Closes #2914

kernel/x86_64/sgemm_direct_skylakex.c

@@ -1,7 +1,8 @@
-#if defined(SKYLAKEX) || defined (COOPERLAKE)
 /* the direct sgemm code written by Arjan van der Ven */
 #include <immintrin.h>
 #include "common.h"
+
+#if defined(SKYLAKEX) || defined (COOPERLAKE)
 /*
  * "Direct sgemm" code. This code operates directly on the inputs and outputs
  * of the sgemm call, avoiding the copies, memory realignments and threading,