phy: amlogic: fix error path in phy_g12a_usb3_pcie_probe()

If clk_prepare_enable() fails we call clk_disable_unprepare()
in the error path what results in a warning that the clock
is disabled and unprepared already.
And if we fail later in phy_g12a_usb3_pcie_probe() then we
bail out w/o calling clk_disable_unprepare().
This patch fixes both errors.

Fixes: 36077e16

 ("phy: amlogic: Add Amlogic G12A USB3 + PCIE Combo PHY Driver")
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/8e416f95-1084-ee28-860e-7884f7fa2e32@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>