drm/amdgpu: rework smu11 i2c for generic operation

Handle things besides EEPROMS.

Signed-off-by: Aaron Rice <wolf@lovehindpa.ws>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Luben Tuikov <luben.tuikov@amd.com>