Fix SDL_GameController API for PSP (#3)

- Add missing mapping
- Make sure the only window has the keyboard focus (so no `SDL_HINT_JOYSTICK_ALLOW_BACKGROUND_EVENTS` is needed)

src/joystick/SDL_gamecontrollerdb.h

@@ -895,6 +895,9 @@ static const char *s_ControllerMappings [] =
 #endif
 #if defined(SDL_JOYSTICK_VITA)
     "50535669746120436f6e74726f6c6c65,PSVita Controller,a:b2,b:b1,back:b10,dpdown:b6,dpleft:b7,dpright:b9,dpup:b8,leftshoulder:b4,leftstick:b14,lefttrigger:a4,leftx:a0,lefty:a1,rightshoulder:b5,rightstick:b15,righttrigger:a5,rightx:a2,righty:a3,start:b11,x:b3,y:b0,",
+#endif
+#if defined(SDL_JOYSTICK_PSP)
+    "505350206275696c74696e206a6f7970,PSP builtin joypad,y:b0,b:b1,a:b2,x:b3,leftshoulder:b4,rightshoulder:b5,dpdown:b6,dpleft:b7,dpup:b8,dpright:b9,back:b10,start:b11,leftx:a0,lefty:a1,rightx:a2,righty:a3,",
 #endif
     "hidapi,*,a:b0,b:b1,back:b4,dpdown:b12,dpleft:b13,dpright:b14,dpup:b11,guide:b5,leftshoulder:b9,leftstick:b7,lefttrigger:a4,leftx:a0,lefty:a1,rightshoulder:b10,rightstick:b8,righttrigger:a5,rightx:a2,righty:a3,start:b6,x:b2,y:b3,",
     NULL

src/video/psp/SDL_pspvideo.c

@@ -214,6 +214,7 @@ PSP_CreateWindow(_THIS, SDL_Window * window)
     /* Setup driver data for this window */
     window->driverdata = wdata;
 
+    SDL_SetKeyboardFocus(window);
 
     /* Window has been successfully created */
     return 0;