Relax LOD computation bounds; add mipmap.2d.projected to mustpass

Relax LOD computation bounds; add mipmap.2d.projected to mustpass

This change updates LOD approximation rules to match proposed spec
language in Vulkan texture filtering and mipmap tests.

dEQP-VK.texture.mipmap.2d.projected.* is added back to the mustpass.

Affects: dEQP-VK.texture.*

Change-Id: Ic786bc733913a76d27f0cba31f3a61a10f8144fc