include: dt-bindings: clock: fix offsets of stm32f7 DCKCFGR registers

All of the following list the registers at 0x8C/0x90:
- RM0431 ('f72x/'f73x)
- RM0385 ('f74x/'f75x)
- RM0410 ('f76x/'f77x)

Signed-off-by: Armin Brauns <armin.brauns@embedded-solutions.at>