uboot-imx

serial: lpuart: support uclass clk api

Modify most APIs to use udevice as the first parameter, then
it will be easy to get the clk reference by using udevice pointer.
Use uclass api to get lpuart clk when CONFIG_CLK is enabled.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Cc: Stefano Babic <sbabic@denx.de>