drm/amd/display: Remove the unused function link_timing_bandwidth_kbps()

The function link_timing_bandwidth_kbps is defined in the
link_validation.c file, but not called elsewhere, so remove this unused
function.

drivers/gpu/drm/amd/amdgpu/../display/dc/link/link_validation.c:258:10: warning: no previous prototype for ‘link_timing_bandwidth_kbps’.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=4547


Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>