[Bug] EEPROM writes inside via_init_kb are erased

Describe the Bug

Loading a custom configuration for VIA is commonly implemented as follows:

void via_init_kb(void) {
	if (via_eeprom_is_valid()) {
		// Read config from EEPROM
	} else {
		// Write default config to EEPROM
	}
}

This will load the configuration from the EEPROM if VIA's magic values are present, otherwise a default configuration will be stored. This works correctly in some cases, however, if the keyboard is restarted after clearing the EEPROM without any further writes to the configuration, a blank configuration will be loaded. Steps to replicate are as follows:

1. Use Bootmagic Lite to reset EEPROM.
2. Reconnect keyboard to exit bootloader. This causes a default custom configuration to be used and saved.
3. Reconnect keyboard without making any changes that cause the custom configuration to be updated. This causes a blank configuration to be loaded.

I believe this is caused by the following:

1. keyboard_init is called which calls via_init which then calls via_init_kb.
2. On returning from via_init_kb, via_init checks to see if the EEPROM is valid and uses eeconfig_init_via to initialise it if not.
3. keyboard_init eventually calls quantum_init which calls magic to check if the EEPROM starts with the magic number (different to VIA's magic values). If the magic number isn't present eeconfig_init is called.
4. eeconfig_init calls eeconfig_init_quantum which calls eeprom_driver_erase to erase the EEPROM, clearing any writes that have already occurred.
5. eeconfig_init_quantum then calls eeconfig_init_via to initialise VIA's EEPROM again, but without calling via_init_kb.

An easy workaround is to save the configuration at a later stage such as within keyboard_post_init_user, although this potentially causes EEPROM writes on every boot. Another workaround would be to write defaults in eeconfig_init_kb and perform reads within keyboard_post_init_user.

Keyboard Used

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Link to product page (if applicable)

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Operating System

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qmk doctor Output

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Is AutoHotKey / Karabiner installed

• AutoHotKey (Windows)
• Karabiner (macOS)

Other keyboard-related software installed

No response

Additional Context

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