platform_camera.h: remove duplicate definitions
	* a1200: CAM_USES_ASPECT_CORRECTION
	* a2100: CAM_UNCACHED_BIT
	* d20:   CAM_STARTUP_CRASH_FILE_OPEN_FIX
	* ixus115_elph100hs: CAM_DRIVE_MODE_FROM_TIMER_MODE
	* ixus300_sd4000: PARAM_CAMERA_NAME
	* sx220hs: DRAW_ON_ACTIVE_BITMAP_BUFFER_ONLY