dts: stm32f1: move dts.fixup to soc family level

This moves and merges the existing board-level dts.fixup files
for STM32 F1 SOC family into one soc family level dts.fixup file.
No new fixup blocks have been added, only fixup blocks, that were
part of at least one board level dts.fixup file are present in
soc family level dts.fixup file.

Contributes to #5707

Signed-off-by: Daniel Wagenknecht <wagenknecht.daniel@gmail.com>