phy: ti-pipe3: cleanup clock handling

As this driver is no longer USB specific, use generic clock names.
- Fix PLL_SD_SHIFT from 9 to 10
- Don't separate prepare/unprepare clock from enable/disable. This
  ensures optimal power savings.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>