sdhci_fdt_spacemit: Avoid setting the 'io' clock

[bnovkov]

Summary

The spacemit SDHCI driver conflated the 'io' clock with the base
SDHCI clock and used in the corresponding 'sdhci_set_clock' interface
method. However, this clock is only meant to limit the maximum speed
of the peripheral. Careful inspection of the corresponding Linux and
(pending) uboot drivers confirms this; the "io" clock is either ignored
or only set during attach and is not touched afterwards.

Fixes: 550db3d6f502

[mhorne]

sys/dev/sdhci/sdhci_fdt_spacemit.c

81

What is this clock then? Should it be the one manipulated by the SDHCI_SET_CLOCK() method?