aes3k: Re-send some commands for each capture

The driver seems to have relied on the device to be fully
deactivated and activated again for each capture. This is not the case
during enroll, and as such in can cause issues.

Try fixing this by splitting out the last few commands send to the
device and assuming that this starts the capture.

Fixes: #306

libfprint/drivers/aes3k.h

@@ -57,4 +57,6 @@ struct _FpiDeviceAes3kClass
   gsize                data_buflen;    /* buffer length of usb bulk transfer */
   struct aes_regwrite *init_reqs;       /* initial values sent to device */
   gsize                init_reqs_len;
+  struct aes_regwrite *capture_reqs;       /* capture values sent to device */
+  gsize                capture_reqs_len;
 };