clk: amlogic: g12a: fix mmc A peripheral clock

The bit index of the peripheral clock for mmc A is wrong
This was probably not a problem for mmc A as the peripheral is likely left
enabled by the bootloader.

No issues has been reported so far but it could be a problem, most likely
some form of conflict between the ethernet and mmc A clock, breaking
ethernet on init.

Use the value provided by the documentation for mmc A before this
becomes an actual problem.

Fixes: 085a4ea9 ("clk: meson: g12a: add peripheral clock controller")
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20241213-amlogic-clk-g12a-mmca-fix-v1-1-5af421f58b64@baylibre.com


Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>