usb: dwc3: gadget: Remove redundant check

dwc3_gadget_init_hw_endpoints calls dwc3_alloc_trb_pool only if epnum is not
equal to 0 or 1. Hence, rechecking it in the called function is redundant.

Signed-off-by: Amit Virdi <amit.virdi@st.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>