usb: gadget: u_bam_data: Fix ordering of tethered disconnect notification

Current ordering is as below:
1. Call IPA tethered function related disconnect notify API
2. Perform USB and IPA BAM related pipe disconnect

Above step 1 deletes USB related depedency graph with IPA RM which
results into IPA is not pulling pending data from USB BAM producer pipe.
Due to this, data stall is observed and USB BAM driver is encountering
condition where it explicitly crashes device using panic().

Fix above order as below:
1. Perform USB and IPA BAM related pipe disconnect
2. Call IPA tethered function related disconnect notify API

With above ordering, USB related depedency graph is deleted after USB
BAM producer pipe is empty and disconnected successfully here.

Change-Id: Ib7e498a789008a44cc3f196064a9c2dda828bb1a
Signed-off-by: Mayank Rana <mrana@codeaurora.org>