clk: imx: Add API for clk unregister when driver probe fail

For i.MX clock drivers probe fail case, clks should be unregistered
in the return path, this patch adds a common API for i.MX clock
drivers to unregister clocks when fail.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>