arch: arm: stm32f2: remove core zephyr header inclusions from soc.h

The stm32f2 version of soc.h misses the changes done in commit
aee97be7 ("arch: arm: soc: remove core zephyr header inclusions
from soc.h").

Signed-off-by: Istvan Bisz <istvan.bisz@t-online.hu>