gallium/st/dri: add dri and pipe cap for image explicit flush

v2: squash "radeonsi: enable PIPE_CAP_EXPLICIT_FLUSH"
    rename cap to PIPE_CAP_EXTERNAL_FLUSH
    added explanation of the cap in screen.rst

Signed-off-by: Tapani Pälli <tapani.palli@intel.com>
48 jobs for !2643 with pipe-cap-flush in 15 minutes and 44 seconds (queued for 5 seconds)
latest detached
Status Job ID Name Coverage
  Container
passed #927145
debian-10:amd64

00:00:28

passed #927147
aarch64
debian-10:arm64

00:00:19

passed #927148
aarch64
debian-10-test:arm64

00:00:22

passed #927146
debian-9:amd64

00:00:21

passed #927144
lava-container:arm64

00:00:24

passed #927143
lava-container:armhf

00:00:24

 
  Build
passed #927150
lava-build:arm64

00:04:23

passed #927149
lava-build:armhf

00:05:02

passed #927153
aarch64
meson-arm64

00:06:16

passed #927152
aarch64
meson-armhf

00:05:41

passed #927155
meson-clang

00:08:58

passed #927158
meson-clover

00:08:22

passed #927159
meson-clover-old-llvm

00:04:11

passed #927161
meson-i386

00:04:48

passed #927151
meson-main

00:10:40

passed #927162
meson-mingw32-x86_64

00:06:44

passed #927154
meson-swr-glvnd

00:04:26

passed #927160
meson-vulkan

00:06:41

passed #927163
scons

00:09:52

passed #927164
scons-old-llvm

00:08:23

passed #927156
scons-swr

00:04:45

passed #927157
scons-win64

00:06:51

 
  Test
passed #927187
db410c
arm64_a306_gles2 1/4

00:03:54

passed #927188
db410c
arm64_a306_gles2 2/4

00:04:52

passed #927189
db410c
arm64_a306_gles2 3/4

00:03:59

passed #927190
db410c
arm64_a306_gles2 4/4

00:04:10

passed #927176
mesa-cheza
arm64_a630_gles2

00:05:08

passed #927177
mesa-cheza
arm64_a630_gles31 1/4

00:04:46

passed #927178
mesa-cheza
arm64_a630_gles31 2/4

00:05:13

passed #927179
mesa-cheza
arm64_a630_gles31 3/4

00:05:22

passed #927180
mesa-cheza
arm64_a630_gles31 4/4

00:05:33

passed #927181
mesa-cheza
arm64_a630_gles3 1/6

00:03:36

passed #927182
mesa-cheza
arm64_a630_gles3 2/6

00:03:44

passed #927183
mesa-cheza
arm64_a630_gles3 3/6

00:03:48

passed #927184
mesa-cheza
arm64_a630_gles3 4/6

00:04:06

passed #927185
mesa-cheza
arm64_a630_gles3 5/6

00:03:56

passed #927186
mesa-cheza
arm64_a630_gles3 6/6

00:03:53

passed #927165
lava-rk3288-veyron-jaq
panfrost-t760-test:armhf

00:06:05

passed #927166
lava-rk3399-gru-kevin
panfrost-t860-test:arm64

00:05:27

passed #927167
test-llvmpipe-gles2 1/4

00:03:48

passed #927168
test-llvmpipe-gles2 2/4

00:04:12

passed #927169
test-llvmpipe-gles2 3/4

00:04:31

passed #927170
test-llvmpipe-gles2 4/4

00:03:31

passed #927171
test-softpipe-gles2 1/4

00:01:50

passed #927172
test-softpipe-gles2 2/4

00:01:36

passed #927173
test-softpipe-gles2 3/4

00:01:50

passed #927174
test-softpipe-gles2 4/4

00:01:30

passed #927175
test-softpipe-gles3-limited

00:03:30