🔧 Define Malyan M300 E0_AUTO_FAN_PIN directly

[thisiskeithb]

Description

Drop the alias for now in preparation for MarlinFirmware/Marlin#27214

Benefits

Upstream CI will pass 😄

Related Issues

• [WIP] 🔧 Revamp AUTO_FAN configuration Marlin#27214

[thinkyhead]

The board provides a pin for this, and we want boards to be able to provide these pins and have them automatically assigned without users needing to know the pin number. So the correct solution (for now) is to leave the pin undefined and let the pins file define it for us.

[thisiskeithb]

The board provides a pin for this, and we want boards to be able to provide these pins and have them automatically assigned without users needing to know the pin number. So the correct solution (for now) is to leave the pin undefined and let the pins file define it for us.

The pins file provides AUTO_FAN_PIN which is not E0_AUTO_FAN_PIN and now this config is unsafe because it no longer enables the hotend cooling fan. I fixed this in MarlinFirmware/Marlin#27214, which is why I was defining the pin directly here to ensure that the hotend auto fan still works for this config while things are hashed out in the linked PR.