vfio: include <linux/slab.h> for kmalloc

The vfio drivers call kmalloc or kzalloc, but do not
include <linux/slab.h>, which causes build errors on
ARM.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Cc: kvm@vger.kernel.org

drivers/vfio/pci/vfio_pci_config.c

@@ -27,6 +27,7 @@
 #include <linux/pci.h>
 #include <linux/uaccess.h>
 #include <linux/vfio.h>
+#include <linux/slab.h>
 
 #include "vfio_pci_private.h"