usb: f_gsi: Ignore supsend/resume events if data interface is not selected

Usually the GSI disconnect handler is invoked on disconnect
and bus suspend (with remote wakeup disabled) conditions.
However, for functions such as MBIM that support alternate
data interface, suspend/resume handling becomes a no-op
if the data interface is not selected. One such example
is disabling/enabling network device from device manager.
This operation explicitly disables data interface
and subsequent suspend/resume operations become no-ops.

CRs-Fixed: 946385

Change-Id: Idaf240ed5253f61880c05a1b11d87d4979d474c9
Signed-off-by: Devdutt Patnaik <dpatnaik@codeaurora.org>