drm/amd/display: Fix minor issues in BW Allocation Phase2

[Why]
Fix minor issues in BW Allocation Phase2.

[How]
- In set_usb4_req_bw_req(), link->dpia_bw_alloc_config.response_ready
  flag should be reset before writing DPCD REQUEST_BW.
- Fix the granularity for value of 2 in get_bw_granularity().
- Removed bandwidth allocation support display fw boot option as
  the fw would read feature enable status from bios.
- Clean up DPIA_EST_BW_CHANGED and DPIA_BW_REQ_SUCCESS cases in
  dpia_handle_bw_alloc_response().
- Removed allocate_usb4_bw and deallocate_usb4_bw.
- Optimized loop in get_lowest_dpia_index().
- Updated link_dp_dpia_allocate_usb4_bandwidth_for_stream() and
  set_usb4_req_bw_req() to always issue request bw.

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: PeiChen Huang <peichen.huang@amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Meenakshikumar Somasundaram <meenakshikumar.somasundaram@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>