The whole joystick list is refreshed anyway, so probably no reason to track the delay per joystick.
Fixes FPS drops happening each 2-3 seconds in Super House of Dead Ninjas. The game normally calls joyGetPosEx() for joystick 0 only, but once per second it scans all the 16 possible joysticks and for 15 of those joyGetPosEx() results in lengthy joystick list refresh, causing FPS drop in this otherwise not demanding game.
-- v2: winmm: Use a global timeout for refreshing joystick devices.