examples/camera: fix build error and still capture logic

Add missing #include <sys/boardctl.h> in camera_bkgd.c to fix
implicit declaration of boardctl() and undeclared BOARDIOC_NX_START.

Also fix capture_num check in camera_main.c to only apply still
capture size enumeration when capture_type is STILL_CAPTURE.

Signed-off-by: wangjianyu3 <wangjianyu3@xiaomi.com>

examples/camera/camera_bkgd.c

@@ -33,6 +33,7 @@
 #include <semaphore.h>
 #include <errno.h>
 #include <debug.h>
+#include <sys/boardctl.h>
 
 #include <arch/board/board.h>
 #include <nuttx/nx/nx.h>

examples/camera/camera_main.c

@@ -537,7 +537,7 @@ int main(int argc, FAR char *argv[])
    * And all allocated memorys are VIDIOC_QBUFed.
    */
 
-  if (capture_num != 0)
+  if (capture_num != 0 && capture_type == V4L2_BUF_TYPE_STILL_CAPTURE)
     {
       /* Determine image size from connected image sensor name,
        * because video driver does not support VIDIOC_ENUM_FRAMESIZES