regression/ck_spinlock: Make sure CORES is at least 2 for ck_hclh.

In ck_hclh, make sure CORES is at least 2, as we then attempt to create
CORES / 2 locks.
This fixes the test when compiling with -DCORES=1.

regressions/ck_spinlock/ck_hclh.h

@@ -2,6 +2,11 @@
 #define LOCK_NAME "ck_clh"
 #define LOCK_DEFINE static ck_spinlock_hclh_t CK_CC_CACHELINE *glob_lock; \
 		    static ck_spinlock_hclh_t CK_CC_CACHELINE *local_lock[CORES / 2]
+#if CORES < 2
+#undef CORES
+#define CORES 2
+#endif
+
 #define LOCK_STATE ck_spinlock_hclh_t *na = malloc(MAX(sizeof(ck_spinlock_hclh_t), 64))
 #define LOCK ck_spinlock_hclh_lock(&glob_lock, &local_lock[(core % CORES) / 2], na)
 #define UNLOCK ck_spinlock_hclh_unlock(&na)