portability cmsis_rtosv2: Check return of k_mem_slab_init()

Instead of trusting blindly that k_mem_slab_init()
will succeed, let's check it, and handle failures
appropriately.
Otherwise, a buffer of garbage will be passed
around, leading to misterious failures later on.

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>

subsys/portability/cmsis_rtos_v2/mempool.c

@@ -68,7 +68,15 @@ osMemoryPoolId_t osMemoryPoolNew(uint32_t block_count, uint32_t block_size,
 		mslab->is_dynamic_allocation = FALSE;
 	}
 
-	k_mem_slab_init(&mslab->z_mslab, mslab->pool, block_size, block_count);
+	int rc = k_mem_slab_init(&mslab->z_mslab, mslab->pool, block_size, block_count);
+
+	if (rc != 0) {
+		k_mem_slab_free(&cv2_mem_slab, (void *) &mslab);
+		if (attr->mp_mem == NULL) {
+			k_free(mslab->pool);
+		}
+		return NULL;
+	}
 
 	if (attr->name == NULL) {
 		strncpy(mslab->name, init_mslab_attrs.name,