drm/amd/display: remove invalid dc_is_hw_initialized function

[why/how]
We found out that the register we read actually gets reset by SMU
after we loose power, meaning this always returns true

Signed-off-by: Joseph Gravenor <joseph.gravenor@amd.com>
Reviewed-by: Eric Yang <eric.yang2@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>