phy: cadence: Sierra: Add missing clk_disable_unprepare() in .remove callback

Add missing clk_disable_unprepare() in cdns_sierra_phy_remove().

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Aswath Govindraju <a-govindraju@ti.com>