usb: misc: Add USB super speed re-driver support

Add redriver support for improving signal quality on some board
designs.

Different board level designs may need to use different parameters,
so expose four interfaces under /sys/kerne/debug for the
tuning, that is eq, flat_gain, output_comp and loss_match.

Change-Id: Ia662fec69063cb676b0511486d09b4cffa57e25a
Signed-off-by: Liangliang Lu <luliang@codeaurora.org>