clover: Add constructor for global_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 svm.
Signed-off-by: Vinson Lee <vlee@freedesktop.org>

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

@@ -453,6 +453,9 @@ void
 kernel::scalar_argument::unbind(exec_context &ctx) {
 }
 
+kernel::global_argument::global_argument() : buf(nullptr), svm(nullptr) {
+}
+
 void
 kernel::global_argument::set(size_t size, const void *value) {
    if (size != sizeof(cl_mem))

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

@@ -167,6 +167,8 @@ namespace clover {
 
       class global_argument : public argument {
       public:
+         global_argument();
+
          virtual void set(size_t size, const void *value);
          virtual void set_svm(const void *value);
          virtual void bind(exec_context &ctx,