arm64: dts: amlogic: s4: assign mmc b clock to 24MHz

The amlogic MMC driver operate with the assumption that MMC clock
is configured to provide 24MHz. It uses this path for low
rates such as 400kHz.

This assumption did hold true until but it now, but it is apparently
not the case with s4. The clock has been reported to provide 1GHz
instead. This is most likely due to how the bootloader is using the MMC
clock on this platform.

Regardless of why the MMC clock rate is 1GHz, if the MMC driver expects
24MHz, the clock should be properly assigned, so assign it.

Reported-by: Nick Xie <nick@khadas.com>
Closes: https://lore.kernel.org/linux-amlogic/20260113011931.40424-1-nick@khadas.com/
Fixes: 3ab9d54 ("arm64: dts: amlogic: enable some device nodes for S4")
Tested-by: Nick Xie <nick@khadas.com>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patch.msgid.link/20260114-amlogic-s4-mmc-fixup-v3-1-a4d3e136b3f2@baylibre.com
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>

Author: jbrun3t

arch/arm64/boot/dts/amlogic/meson-s4.dtsi

@@ -838,6 +838,9 @@
 			clock-names = "core", "clkin0", "clkin1";
 			resets = <&reset RESET_SD_EMMC_B>;
 			status = "disabled";
+
+			assigned-clocks = <&clkc_periphs CLKID_SD_EMMC_B>;
+			assigned-clock-rates = <24000000>;
 		};
 
 		emmc: mmc@fe08c000 {