usb: gadget: f_gsi: Use local variables to avoid crossing 80 characters

Use local variables in ipa_connect_channels() function to avoid
crossing the 80 characters column limit. This also ensures
better code readability.

Change-Id: I9cc1735b9fa8d1c1d9c46369c7eb0763250d3721
Signed-off-by: Azhar Shaikh <azhars@codeaurora.org>