Add workaround to make Pokemon Snap controls working and images selectable

The controller problem seems to be related to the graphics plugin. A quote from
darkmaster14

"I believe the Pokemon Snap input issue is closely related to the missing red
 dot issue. If you recall, in the original hardware, when you first arrive on
 the beach, there's a small tutorial where you can't move the cursor until you
 take a picture of the first few Pokemon that show up. Once you finish the mini
 tutorial, you can move the cursor around as you please. Well, the red dot
 doesn't work on most plugins, so the game doesn't detect the cursor locking
 onto the first few Pokemon, so the tutorial doesn't work, and thus the input
 never gets unlocked.

 Well, I got a hold of a very buggy port of FatCat's software renderer plugin
 for Mupen64Plus, and the red dot works on that, which lets you do the tutorial,
 and thus the cursor movement is unlocked and you can play the game as normal.
 So really, the problem most likely lies in the video plugins rather than the
 emulation core. I'm guessing on Project64, however, they added a hack to force
 the cursor to move around despite the red dot not working, which is why it
 works on that emulator."
Add missing read mode check in flashram_command -> execute