lima: fix handling of reverse depth range

Looks like we need to handle cases when near > far and near == far. In first case we just need to swap near and far, and in second we need subtract epsilon from near if it's not zero.

Fixes 10 tests in dEQP-GLES2.functional.depth_range.*

Signed-off-by: Vasily Khoruzhick anarsoul@gmail.com