zink: remove batch count threshold for maybe flush

this is, if one stops to think about it a moment, not ever going to work
because the batch count can never decrease, meaning that if the threshold
is ever reached, every single draw/compute will trigger a full reset and
then the explosions begin

Fixes: d3734ae2 ("zink: relax maybe_flush batch count threshold")
37 jobs for !10410 with zink-unflush in 8 seconds (queued for 4 seconds)
latest detached
Status Job ID Name Coverage
  Sanity
passed #9122903
sanity

00:00:08

 
  Container
manual #9122908
aarch64 manual
arm_build
manual #9122910
windows shell 1809 mesa manual
windows_build_vs2019
manual #9122905
manual
x86_build-base
manual #9122907
manual
x86_test-base
 
  Container 2
created #9122920
android_build
created #9122914
i386_build
created #9122926
kernel+rootfs_amd64
created #9122928
aarch64
kernel+rootfs_arm64
created #9122930
aarch64
kernel+rootfs_armhf
created #9122916
ppc64el_build
created #9122918
s390x_build
created #9122912
x86_build
created #9122922
x86_test-gl
created #9122924
x86_test-vk
 
  Meson X86 64
created #9122944
meson-clang
created #9122946
meson-clover
created #9122937
meson-clover-testing
created #9122939
meson-gallium
created #9122942
meson-release
created #9122933
meson-testing
created #9122935
meson-testing-asan
created #9122948
meson-vulkan
 
  Build Misc
created #9122950
arm_test
created #9122952
meson-android
created #9122956
aarch64
meson-arm64
created #9122959
aarch64
meson-arm64-asan
created #9122961
aarch64
meson-arm64-build-test
created #9122954
aarch64
meson-armhf
created #9122964
meson-i386
created #9122970
meson-mingw32-x86_64
created #9122968
meson-ppc64el
created #9122966
kvm
meson-s390x
 
  Layered Backends
created #9122978
zink-lvp-gl
created #9122974
zink-lvp-gles2
created #9122976
zink-lvp-gles3
created #9122972
zink-piglit-quick_gl