freedreno/a6xx: don't enable early-z/lrz if no z-test

freedreno/a6xx: don't enable early-z/lrz if no z-test

But if shader explicitly asks for early-fragment-tests, obey it's
wishes.

Fixes a handful of skia (skqp) CTS fails (9.0_r12)

* gles_bug593049
* gles_circular_arcs_fill
* gles_circular_arcs_stroke_and_fill_square
* gles_clippedcubic2
* gles_complexclip2_path_bw
* gles_complexclip2_rrect_bw
* gles_complexclip3_complex
* gles_complexclip3_simple
* gles_crbug_691386
* gles_cubicclosepath
* gles_cubicpath
* gles_degeneratesegments
* gles_filltypespersp
* gles_innershapes_bw
* gles_inverse_paths
* gles_mixedtextblobs
* gles_onebadarc
* gles_quadclosepath
* gles_quadpath
* gles_rrect_clip_bw
* gles_scale-pixels
* gles_scaledstrokes
* gles_squarehair
* gles_strokes_zoomed
* gles_windowrectangles

Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5907>