Report PS3 accelerometer values in m/s2 instead of Gs

(cherry picked from commit 0467301baf57389d96fafbe169fb07f4c10169bc)

src/joystick/hidapi/SDL_hidapi_ps3.c

@@ -311,7 +311,7 @@ static float HIDAPI_DriverPS3_ScaleAccel(Sint16 value)
 {
     /* Accelerometer values are in big endian order */
     value = SDL_SwapBE16(value);
-    return (float)(value - 511) / 113.0f;
+    return ((float)(value - 511) / 113.0f) * SDL_STANDARD_GRAVITY;
 }
 
 static void HIDAPI_DriverPS3_HandleMiniStatePacket(SDL_Joystick *joystick, SDL_DriverPS3_Context *ctx, Uint8 *data, int size)