drm/amd/pm: remove deprecated I2C_CLASS_SPD support from newly added SMU_14_0_2

Support for I2C_CLASS_SPD  is currently being removed from the kernel.
Only remaining step is to remove the definition of I2C_CLASS_SPD.
Setting I2C_CLASS_SPD  in a driver is a no-op meanwhile, so remove it
here.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>