Set NEAREST filtering for sparse clamp lookup texture

Set NEAREST filtering for sparse clamp lookup texture

Integer formats can't use LINEAR filtering here, so this was
a spec violation.

Given that LINEAR isn't being tested, just use NEAREST in all cases
to avoid complexity.

For the min filter use NEAREST_MIPMAP_NEAREST since mipmaps are used
by the test.

Affects:
KHR-GL46.sparse_texture_clamp_tests.SparseTextureClampLookupResidency
KHR-GL46.sparse_texture_clamp_tests.SparseTextureClampLookupColor

Components: OpenGL
VK-GL-CTS issue: 3653

Change-Id: I5bb7fcde24c4d3dcf0584bf91e96c4c5559b2b39