In prts of the code, we use rcc node "clocks" property to testify the
use of device tree for clocks configuration.
This doesn't work in case of stm32h7 m4 targets as for those,
"upstream rcc" clock configuration, such as sysclk source selection,
is done on m7 core and hence rcc node doesn't have a "clocks"
property.
To work around this, use alternate "d1cpre" property in case of
stm32h7 targets.
Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>
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