usb: gadget: f_gps: Fix no responses on suspend/resume

In the case where the host pc is put to sleep, the
device is suspended and the previous gps session is
teared down by the modem. Upon host pc wakeup a new
session is started by the modem, but the u_glink
driver still has the context for the previous session
resulting in no communication between the modem and
the driver.
Fix this by closing the previous session on receiving
REMOTE_DISCONNECTED and start a new session on
resume if the session is teared now on suspend.

Change-Id: Ibf2d9c35b62691e067cc835fd875248b89323df5
Signed-off-by: Sriharsha Allenki <sallenki@codeaurora.org>