usb: phy: mxs: change description of usb device speed

Change "high speed" to "HS"
Change "non-high speed" to "FS/LS"

Implementation of notify_suspend and notify_resume will be different
according to mxs_phy_data->flags.

Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>