drivers: pinctrl: enable the AFIO clock on the CH32V003/20x/30x

[nzmichaelh]

The Alternate Function IO (AFIO) block must have the clock enabled before use. Some remappings seem to work without, but some like EXTI do not. Fix.

This is the same as #83353 and parts of #87397 but moves the definition to Devicetree.

This is needed by the GPIO EXTI support in #89139

[nzmichaelh]

@recalci FYI

[VynDragon]

I prefer this one and it seems it seems it hasnt broken anything on linkW.

[Copilot]

Pull Request Overview

This PR ensures that the AFIO block clock is enabled via the clock control subsystem rather than relying on in-function remapping logic, which is necessary for proper EXTI support. Key changes include removing the direct clock enable in pin configuration and introducing a dedicated SYS_INIT-based clock initialization function.

• Removed inline clock enabling in pin configuration.
• Added a new clock initialization function that leverages device tree settings.
• Applied the changes consistently across both CH32V003 and CH32V20x/30x drivers.

Reviewed Changes

Copilot reviewed 2 out of 4 changed files in this pull request and generated 2 comments.

File	Description
drivers/pinctrl/pinctrl_wch_afio.c	Removed direct clock enable from pin configuration and added a dedicated clock initialization function with SYS_INIT
drivers/pinctrl/pinctrl_wch_20x_30x_afio.c	Applied similar clock initialization changes consistent with the CH32V003 implementation

Files not reviewed (2)

• dts/riscv/wch/ch32v0/ch32v003.dtsi: Language not supported
• dts/riscv/wch/ch32v208/ch32v208.dtsi: Language not supported