drm/amd/display: Refactor and fix link_dpms I2C

drm/amd/display: Refactor and fix link_dpms I2C

[Why]
link_dpms.c issues I2C writes during HDMI link enablement. Current
implementation contains a lot of duplicated code with copy-paste
errors.

[How]
* Refactor common logic into helper functions.
* Invert logic with early returns to decrease indentation.
* Sequence writes by looping over data arrays.
* Fix write_i2c_retimer_setting is_over_340mhz checking reg_settings
instead of reg_settings_6g in the i2c_reg_index <= 0x20 check.

Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Signed-off-by: Dominik Kaszewski <dominik.kaszewski@amd.com>
Signed-off-by: Ray Wu <ray.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>