freedreno/a6xx: Remove redundant NULL check

This should never happen, and the way build_vbo_state() worked before,
we would've hit a NULL-deref in this case.  Remove the check.

Part-of: <mesa/mesa!5337>
43 jobs for !5337 with remove-vbo-null-check
latest detached
Status Job ID Name Coverage
  Container
manual #3070552
aarch64 manual
arm_build
manual #3070554
manual
arm_test-base
manual #3070555
windows shell 1809 mesa manual
windows_build_vs2019
manual #3070547
manual
x86_build-base
manual #3070550
manual
x86_build_old
manual #3070549
manual
x86_test-base
 
  Container 2
created #3070568
arm64_test
created #3070560
i386_build
created #3070561
ppc64el_build
created #3070563
s390x_build
created #3070558
x86_build
created #3070565
x86_test-gl
created #3070566
x86_test-vk
 
  Meson X86 64
created #3070575
meson-clang
created #3070574
meson-classic
created #3070577
meson-clover
created #3070578
meson-clover-old-llvm
created #3070572
meson-gallium
created #3070570
meson-testing
created #3070580
meson-vulkan
 
  Scons
created #3070581
allowed to fail
scons-win64
 
  Meson Misc
created #3070585
aarch64
meson-arm64
created #3070587
aarch64
meson-arm64-build-test
created #3070583
aarch64
meson-armhf
created #3070591
meson-i386
created #3070596
meson-mingw32-x86_64
created #3070594
kvm
meson-ppc64el
created #3070592
kvm
meson-s390x
created #3070588
docker windows 1809 mesa
meson-windows-vs2019
 
  Freedreno
created #3070614
google-freedreno-db410c
arm64_a306_gles2
created #3070616
google-freedreno-db410c
arm64_a306_gles3
created #3070618
google-freedreno-db410c
arm64_a306_gles3_options
created #3070620
google-freedreno-db820c
arm64_a530_gles2
created #3070623
google-freedreno-db820c
arm64_a530_gles3
created #3070624
google-freedreno-db820c
arm64_a530_gles31
created #3070606
google-freedreno-cheza
arm64_a630_bypass
created #3070598
google-freedreno-cheza
arm64_a630_gles2
created #3070602
google-freedreno-cheza
arm64_a630_gles3
created #3070600
google-freedreno-cheza
arm64_a630_gles31
created #3070608
google-freedreno-cheza
arm64_a630_gmem
created #3070604
google-freedreno-cheza
arm64_a630_noubo
created #3070610
google-freedreno-cheza
arm64_a630_vk
created #3070612
google-freedreno-cheza
arm64_a630_vk_sysmem