This patch is in preparation for adding PM support dwc3 driver. We want to re-use dwc3_core_init and dwc3_core_exit() functions on resume() and suspend() callbacks respectively. Moving even buffer allocation away from dwc3_core_init() will allow us to reuse the event buffer which was allocated long ago on our probe() routine. Signed-off-by: Felipe Balbi <balbi@ti.com>