usb: f_gsi: Don't enable IPA data path if connect channel fails

ipa_connect_channels can return failure if gsi prepare trbs fail or
start xfer fails. But currently driver is not checking for the failure
and goes ahead to enable IPA data path. This leads the controller to
access faulty addresses which cause kernel panic. Fix this by checking
the failure returned from ipa_connect_channels. Also cleanup the error
handling path.

Change-Id: Ia1e8e17381e12231d8d78224ba3b07081f143212
Signed-off-by: Pratham Pratap <prathampratap@codeaurora.org>