drm/amd/include: Add hdmi_redriver_set to atomfirmware

We'll need this for a some upcoming display changes

Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>