drm/amd/display: fix a UBSAN warning in DML2.1

In the Linux kernel, the following vulnerability has been resolved:

drm/amd/display: fix a UBSAN warning in DML2.1

When programming phantom pipe, since cursor_width is explicity set to 0,
this causes calculation logic to trigger overflow for an unsigned int
triggering the kernel's UBSAN check as below:

[ 40.962845] UBSAN: shift-out-of-bounds in /tmp/amd.EfpumTkO/amd/amdgpu/../display/dc/dml2/dml21/src/dml2_core/dml2_core_dcn4_calcs.c:3312:34
[ 40.962849] shift exponent 4294967170 is too large for 32-bit type 'unsigned int'
[ 40.962852] CPU: 1 PID: 1670 Comm: gnome-shell Tainted: G W OE 6.5.0-41-generic #41~22.04.2-Ubuntu
[ 40.962854] Hardware name: Gigabyte Technology Co., Ltd. X670E AORUS PRO X/X670E AORUS PRO X, BIOS F21 01/10/2024
[ 40.962856] Call Trace:
[ 40.962857] <TASK>
[ 40.962860] dump_stack_lvl+0x48/0x70
[ 40.962870] dump_stack+0x10/0x20
[ 40.962872] __ubsan_handle_shift_out_of_bounds+0x1ac/0x360
[ 40.962878] calculate_cursor_req_attributes.cold+0x1b/0x28 [amdgpu]
[ 40.963099] dml_core_mode_support+0x6b91/0x16bc0 [amdgpu]
[ 40.963327] ? srso_alias_return_thunk+0x5/0x7f
[ 40.963331] ? CalculateWatermarksMALLUseAndDRAMSpeedChangeSupport+0x18b8/0x2790 [amdgpu]
[ 40.963534] ? srso_alias_return_thunk+0x5/0x7f
[ 40.963536] ? dml_core_mode_support+0xb3db/0x16bc0 [amdgpu]
[ 40.963730] dml2_core_calcs_mode_support_ex+0x2c/0x90 [amdgpu]
[ 40.963906] ? srso_alias_return_thunk+0x5/0x7f
[ 40.963909] ? dml2_core_calcs_mode_support_ex+0x2c/0x90 [amdgpu]
[ 40.964078] core_dcn4_mode_support+0x72/0xbf0 [amdgpu]
[ 40.964247] dml2_top_optimization_perform_optimization_phase+0x1d3/0x2a0 [amdgpu]
[ 40.964420] dml2_build_mode_programming+0x23d/0x750 [amdgpu]
[ 40.964587] dml21_validate+0x274/0x770 [amdgpu]
[ 40.964761] ? srso_alias_return_thunk+0x5/0x7f
[ 40.964763] ? resource_append_dpp_pipes_for_plane_composition+0x27c/0x3b0 [amdgpu]
[ 40.964942] dml2_validate+0x504/0x750 [amdgpu]
[ 40.965117] ? dml21_copy+0x95/0xb0 [amdgpu]
[ 40.965291] ? srso_alias_return_thunk+0x5/0x7f
[ 40.965295] dcn401_validate_bandwidth+0x4e/0x70 [amdgpu]
[ 40.965491] update_planes_and_stream_state+0x38d/0x5c0 [amdgpu]
[ 40.965672] update_planes_and_stream_v3+0x52/0x1e0 [amdgpu]
[ 40.965845] ? srso_alias_return_thunk+0x5/0x7f
[ 40.965849] dc_update_planes_and_stream+0x71/0xb0 [amdgpu]

Fix this by adding a guard for checking cursor width before triggering
the size calculation.