clk: JZ4780: Add functions for enable and disable USB PHY.

Add new functions to "jz4780_otg_phy_ops" to enable or disable the
USB PHY in the JZ4780 SoC.

Tested-by: 周正 (Zhou Zheng) <sernia.zhou@foxmail.com>
Signed-off-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com>
Link: https://lore.kernel.org/r/20200630163852.47267-2-zhouyanjie@wanyeetech.com


Signed-off-by: Stephen Boyd <sboyd@kernel.org>