usdhc's clock rate is different according to different devices
connected, so clock rate assignment should be placed in board
DT according to different devices connected on each usdhc port.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Abel Vesa <abel.vesa@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

The SolidRun Hummingboard Pulse carrier board carries the SolidRun
i.MX8MQ based SOM.

Notably missing is PCIe support that depends on analog PLLOUT clock.
Current imx clk driver does not support this clock.

Signed-off-by: Jon Nettleton <jon@solid-run.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>