clover: Add constructor for constant_argument.

Fix defects reported by Coverity Scan.

member_not_init_in_gen_ctor: The compiler-generated constructor for this class does not initialize buf.
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>
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10399>

src/gallium/frontends/clover/core/kernel.cpp

@@ -537,6 +537,9 @@ void
 kernel::local_argument::unbind(exec_context &ctx) {
 }
 
+kernel::constant_argument::constant_argument() : buf(nullptr), st(nullptr) {
+}
+
 void
 kernel::constant_argument::set(size_t size, const void *value) {
    if (size != sizeof(cl_mem))

src/gallium/frontends/clover/core/kernel.hpp

@@ -195,6 +195,8 @@ namespace clover {
 
       class constant_argument : public argument {
       public:
+         constant_argument();
+
          virtual void set(size_t size, const void *value);
          virtual void bind(exec_context &ctx,
                            const module::argument &marg);