drm/amd/display: eliminate clock manager code duplication

drm/amd/display: eliminate clock manager code duplication

[Why]
Clock manager contained significant duplicate code between
variants with identical logic for functions using only SMU
calls or shared registers. This increases maintenance overhead
and potential for bugs.

[How]
Expose clock constants and internal functions in header for
sharing. Remove duplicate implementations and update function
pointers to use shared functions. Refactor remaining
variant-specific functions to use shared constants and helper
functions. Add compatibility comments for hardware differences.

Reviewed-by: Dmytro Laktyushkin <dmytro.laktyushkin@amd.com>
Signed-off-by: Gabe Teeger <gabe.teeger@amd.com>
Signed-off-by: Chuanyu Tseng <chuanyu.tseng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>