tests/kms_display_modes: Remove negative test for extended display

This negative test was crated to validate ENOSPC when two 2k-4k or 4k-4k
monitors connected through MST to cover bandwidth issue in MST config.

But it will not helpfult to handle current bandwidth which are
DisplayPort (DP) 1.4 supports a total bandwidth of 4 × 8.1 Gbps.

However, with DP 2.1, the bandwidth allocation strategy has
significantly changed to 4 × 20 Gbps of available bandwidth.
This provides significantly greater display capabilities
w.r.t bandwidth.

v2: Fix compilation issue.
v3: Rebase chagnes.

Signed-off-by: Mohammed Thasleem <mohammed.thasleem@intel.com>
Reviewed-by: Jeevan B <jeevan.b@intel.com>