sdhci: rockchip: Enable HS200 on the RK3399

[manu]

Summary

Pin the xin clock to 200MHz, use the generic UHS timing and tuning
methods, parse the eMMC properties and the vqmmc supply from the device
tree, and set the I/O voltage through the regulator framework instead of
the S18 bit. Limit the RockPro64 to 100MHz.

[mmel]

sys/dev/sdhci/sdhci_fdt_rockchip.c

299

rounding should be used - clk_set_freq(sc->clk_xin, 200000000, CLK_SET_ROUND_DOWN);

308

It is expected that the CRU can always produce the exact frequency. If so, the clk_set_freq() should use the CLK_SET_ROUND_EXACT.

324

helper is part of softc, thus cleared

[manu]

Address mmel's comments