Add SWD pinmux to STM32F1 MCU family .dtsi

[alteman]

Is your enhancement proposal related to a problem? Please describe.
Currently STM32F1 .dtsi files are missing SWD pinmux definitions.

Describe the solution you'd like
PR in hal_stm32 to add SWD pins to the f1 .dtsi files: zephyrproject-rtos/hal_stm32#247

Mentioning maintainer: @erwango

[github-actions]

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[erwango]

Merged.