arm64: dts: allwinner: H6: Allow up to 150 MHz MMC bus frequency

The H6 manual explicitly lists a frequency limit of 150 MHz for the bus
frequency of the MMC controllers. So far we had no explicit limits in the
DT, which limited eMMC to the spec defined frequencies, or whatever the
driver defines (both Linux and FreeBSD use 52 MHz here).

Put those maximum frequencies in the SoC .dtsi, to allow higher speed
modes (which still would need to be explicitly enabled, per board).

Tested with an eMMC using HS-200 on a Pine H64. Running at the spec'ed
200 MHz indeed fails with I/O errors, but 150 MHz seems to work stably.

Fixes: 8f54bd15 ("arm64: allwinner: h6: add device tree nodes for MMC controllers")
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20210113152630.28810-6-andre.przywara@arm.com