lib: Add support for DigitalPersona URU4500

By adding native encryption support, rather than poking at
the firmware to disable it.

This also makes the URU4000B use native encryption.

https://bugs.freedesktop.org/show_bug.cgi?id=55351

libfprint/fp_internal.h

@@ -28,6 +28,8 @@
 
 #include <fprint.h>
 
+#define array_n_elements(array) (sizeof(array) / sizeof(array[0]))
+
 #define container_of(ptr, type, member) ({                      \
         const typeof( ((type *)0)->member ) *__mptr = (ptr);    \
         (type *)( (char *)__mptr - offsetof(type,member) );})