clover: Add constructor for sampler_argument.

Fix defects reported by Coverity Scan.

member_not_init_in_gen_ctor: The compiler-generated constructor for this class does not initialize s.
member_not_init_in_gen_ctor: The compiler-generated constructor for this class does not initialize st.

Signed-off-by: Vinson Lee <vlee@freedesktop.org>
36 jobs for !8657 with fix-cid-1213937 in 11 seconds (queued for 2 seconds)
detached
Status Job ID Name Coverage
  Sanity
passed #6829689
sanity

00:00:11

 
  Container
manual #6829692
aarch64 manual
arm_build
manual #6829693
manual
arm_test-base
manual #6829694
windows shell 1809 mesa manual
windows_build_vs2019
manual #6829690
manual
x86_build-base
manual #6829691
manual
x86_test-base
 
  Container 2
created #6829702
android_build
created #6829705
arm64_test
created #6829706
armhf_test
created #6829699
i386_build
created #6829695
kernel+rootfs_amd64
created #6829696
aarch64
kernel+rootfs_arm64
created #6829697
aarch64
kernel+rootfs_armhf
created #6829700
ppc64el_build
created #6829701
s390x_build
created #6829698
x86_build
created #6829703
x86_test-gl
created #6829704
x86_test-vk
 
  Meson X86 64
created #6829712
meson-clang
created #6829713
meson-clover
created #6829709
meson-clover-testing
created #6829710
meson-gallium
created #6829711
meson-release
created #6829707
meson-testing
created #6829708
meson-testing-asan
created #6829714
meson-vulkan
 
  Build Misc
created #6829715
meson-android
created #6829717
aarch64
meson-arm64
created #6829718
aarch64
meson-arm64-build-test
created #6829716
aarch64
meson-armhf
created #6829720
meson-i386
created #6829723
meson-mingw32-x86_64
created #6829722
kvm
meson-ppc64el
created #6829721
kvm
meson-s390x
created #6829719
allowed to fail
scons-win64
 
  Software Renderer
created #6829724
llvmpipe-piglit-cl