usb: gadget: f_fs: Add support for ipc logging

Log function entry and exit and dump relevant values
into ipc log buffer. This allows to debug various
race conditions and stability issues.

Change-Id: I15011d79fc2f054e64f8bbd1f8f5db8944b46ada
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>