usb: gadget: f_gsi: Avoid calling suspend again in case of func suspend

If the function is in USB3 function suspend state, skip suspend.
Suspend is handled by function suspend routine.

Change-Id: Ieaf58efbe9bc45043738aa1fc297a79f09ae8729
Signed-off-by: Azhar Shaikh <azhars@codeaurora.org>