avutil/hwcontext_cuda: increase CUDA frame alignment to 512

At least on Turing, a frame without 512 byte alignment cannot be passed
to cuTexObjectCreate.

libavutil/hwcontext_cuda.c

@@ -30,7 +30,7 @@
 #include "pixfmt.h"
 #include "imgutils.h"
 
-#define CUDA_FRAME_ALIGNMENT 256
+#define CUDA_FRAME_ALIGNMENT 512
 
 typedef struct CUDAFramesContext {
     int shift_width, shift_height;