drm/amd/pm: Remove I2C_CLASS_SPD support

I2C_CLASS_SPD was used to expose the EEPROM content to user space,
via the legacy eeprom driver. Now that this driver has been removed,
we can remove I2C_CLASS_SPD support. at24 driver with explicit
instantiation should be used instead.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>