usb/ssb: Add missing #include <linux/slab.h>

m68k/allmodconfig:

drivers/usb/host/ssb-hcd.c: In function ‘ssb_hcd_probe’:
drivers/usb/host/ssb-hcd.c:170: error: implicit declaration of function ‘kzalloc’
drivers/usb/host/ssb-hcd.c:170: warning: assignment makes pointer from integer without a cast
drivers/usb/host/ssb-hcd.c:205: error: implicit declaration of function ‘kfree’
Signed-off-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/ssb-hcd.c

@@ -22,6 +22,7 @@
 #include <linux/delay.h>
 #include <linux/platform_device.h>
 #include <linux/module.h>
+#include <linux/slab.h>
 #include <linux/usb/ehci_pdriver.h>
 #include <linux/usb/ohci_pdriver.h>