zink: restore previous semaphore (prev_sem) handling

this was accidentally lost during refactoring

Fixes: fa36a16c ("zink: make timeline semaphores per-screen")

Reviewed-by: Dave Airlie <airlied@redhat.com>
Part-of: <!10421>
37 jobs for !10421 with zink-prev_sem in 9 minutes and 52 seconds (queued for 2 seconds)
latest detached
Status Job ID Name Coverage
  Sanity
passed #9145919
sanity

00:00:10

 
  Container
passed #9145924
aarch64
arm_build

00:00:35

passed #9145926
windows shell 1809 mesa
windows_build_vs2019

00:00:09

passed #9145920
x86_build-base

00:00:23

passed #9145922
x86_test-base

00:00:21

 
  Container 2
passed #9145935
android_build

00:00:23

passed #9145930
i386_build

00:00:25

passed #9145940
kernel+rootfs_amd64

00:00:25

passed #9145942
aarch64
kernel+rootfs_arm64

00:00:56

passed #9145944
aarch64
kernel+rootfs_armhf

00:00:18

passed #9145932
ppc64el_build

00:00:23

passed #9145934
s390x_build

00:00:21

passed #9145928
x86_build

00:00:23

passed #9145937
x86_test-gl

00:00:24

passed #9145938
x86_test-vk

00:00:22

 
  Meson X86 64
passed #9145956
meson-clang

00:08:48

passed #9145958
meson-clover

00:01:50

passed #9145950
meson-clover-testing

00:01:46

passed #9145952
meson-gallium

00:05:07

passed #9145954
meson-release

00:03:18

passed #9145946
meson-testing

00:01:43

passed #9145948
meson-testing-asan

00:02:39

passed #9145960
meson-vulkan

00:03:43

 
  Build Misc
passed #9145962
arm_test

00:01:04

passed #9145964
meson-android

00:01:12

passed #9145968
aarch64
meson-arm64

00:01:53

passed #9145971
aarch64
meson-arm64-asan

00:03:38

passed #9145973
aarch64
meson-arm64-build-test

00:01:18

passed #9145966
aarch64
meson-armhf

00:02:00

passed #9145974
meson-i386

00:01:50

passed #9145977
meson-mingw32-x86_64

00:02:54

passed #9145976
meson-ppc64el

00:02:02

passed #9145975
kvm
meson-s390x

00:03:40

 
  Layered Backends
passed #9145981
zink-lvp-gl

00:01:51

passed #9145979
zink-lvp-gles2

00:02:59

passed #9145980
zink-lvp-gles3

00:02:09

passed #9145978
zink-piglit-quick_gl

00:03:22