lima: fix handling of reverse depth range

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.*

Reviewed-by: Qiang Yu <yuq825@gmail.com>
Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3400>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3400>