i965: Only magnify depth for 3D textures, not array textures.

i965: Only magnify depth for 3D textures, not array textures.

When BaseLevel > 0, we magnify the dimensions to fill out the size of
miplevels [0..BaseLevel).  In particular, this was magnifying depth,
thinking that the depth doubles at each level.  This is perfectly
reasonable for 3D textures, but dead wrong for array textures.

Changing the depth != 1 condition to a target == GL_TEXTURE_3D check
should make this only happen in the appropriate cases.

Fixes about 32 dEQP tests:
- dEQP-GLES31.functional.texture.gather.*.level_{1,2}

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Cc: mesa-stable@lists.freedesktop.org