V4L/DVB: em28xx: adjust number of packets per URB

Increase the packets per URB count from 40 to 64.  I suspect that whoever was
looking at the usbsnoop captures saw "0x40" packets and mistook it for "40".

As a result of this change, I can see a 25% reduction in the number of
interrupts generated via powertop.

This work was sponsored by EyeMagnet Limited.
Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/em28xx/em28xx.h

@@ -140,10 +140,10 @@
 #define EM28XX_NUM_BUFS 5
 
 /* number of packets for each buffer
-   windows requests only 40 packets .. so we better do the same
+   windows requests only 64 packets .. so we better do the same
    this is what I found out for all alternate numbers there!
  */
-#define EM28XX_NUM_PACKETS 40
+#define EM28XX_NUM_PACKETS 64
 
 #define EM28XX_INTERLACED_DEFAULT 1