nv30: Fix non-scissored clears after a scissor has been set

Additionally add support for PIPE_CAP_CLEAR_SCISSORED since we are already
touching the scissor state.

Fixes various gnome-shell rendering artifacts.
47 jobs for !12154 with bugfix/nv30_scissored_clear in 8 seconds (queued for 11 seconds)
detached
Status Job ID Name Coverage
  Sanity
passed sanity #12376917

00:00:08

 
  Container
manual debian/arm_build #12376920
aarch64 manual
manual debian/x86_build-base #12376918
manual
manual debian/x86_test-base #12376919
manual
manual fedora/x86_build #12376921
manual
manual windows_build_vs2019 #12376922
windows shell 1809 mesa manual
 
  Container 2
created debian/android_build #12376927
created debian/i386_build #12376924
created debian/ppc64el_build #12376925
created debian/s390x_build #12376926
created debian/x86_build #12376923
created debian/x86_test-gl #12376928
created debian/x86_test-vk #12376929
created kernel+rootfs_amd64 #12376930
created kernel+rootfs_arm64 #12376931
aarch64
created kernel+rootfs_armhf #12376932
aarch64
 
  Build X86 64
created debian-clang #12376939
created debian-clover #12376940
created debian-clover-testing #12376935
created debian-gallium #12376936
created debian-release #12376937
created debian-testing #12376933
created debian-testing-asan #12376934
created debian-vulkan #12376941
created fedora-release #12376938
 
  Build Misc
created debian-android #12376943
created debian-arm64 #12376945
aarch64
created debian-arm64-asan #12376946
aarch64
created debian-arm64-build-test #12376947
aarch64
created debian-armhf #12376944
aarch64
created debian/arm_test #12376942
created debian-i386 #12376948
created debian-mingw32-x86_64 #12376950
created debian-ppc64el #12376949
 
  Intel
created i915-g33-deqp #12376951
anholt-g33 manual
created i915-g33-khr-deqp #12376952
anholt-g33 manual
created i915-g33-piglit #12376953
anholt-g33 manual
created i915-g33-traces #12376954
anholt-g33 manual
created iris-apl-gl #12376955
mesa-ci-x86-64-lava-asus-C523NA-A20057-coral manual
created iris-glk-egl #12376960
mesa-ci-x86-64-lava-hp-x360-12b-n4000-octopus manual
created iris-glk-gl #12376959
mesa-ci-x86-64-lava-hp-x360-12b-n4000-octopus manual
created iris-glk-gles2 #12376956
mesa-ci-x86-64-lava-hp-x360-12b-n4000-octopus manual
created iris-glk-gles3 #12376957
mesa-ci-x86-64-lava-hp-x360-12b-n4000-octopus manual
created iris-glk-gles31 #12376958
mesa-ci-x86-64-lava-hp-x360-12b-n4000-octopus manual
created iris-glk-traces #12376961
mesa-ci-x86-64-lava-hp-x360-12b-n4000-octopus manual
created iris-kbl-traces #12376962
mesa-ci-x86-64-lava-hp-x360-14-G1-sona manual
 
  Freedreno
created a530_piglit_gl #12376963
google-freedreno-db820c manual