phy: sun4i-usb: Remove usb_clk_cfg set in probe

usb_clk_cfg is setting CTRL_PHYGATE bit value in probe
which is BIT 0 for sun4i, 6i and 8 for a83t but all
these were handling in phy ops init exit calls.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Tested-by: Jagan Teki <jagan@amarulasolutions.com>