Calibrate the USB PHY TX settings to pass the eye diagram signal
integrity test.  The settings are taken from the i.MX6 reference
manual's recommended configuration for USB certification (66.2.6).
Signed-off-by: NJaret Cantu <jaret.cantu@timesys.com>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>