This patch fixes these GCC warnings.

create-context-from-type.c: In function ‘piglit_cl_test’:
create-context-from-type.c:173:24: warning: variable ‘invalid_platform_context_properties’ set but not used [-Wunused-but-set-variable]
  cl_context_properties invalid_platform_context_properties[] = {
                        ^
create-context-from-type.c:156:13: warning: unused variable ‘cl_ctx’ [-Wunused-variable]
  cl_context cl_ctx;
             ^
create-context-from-type.c:155:9: warning: unused variable ‘errNo’ [-Wunused-variable]
  cl_int errNo;
         ^

Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Tom Stellard <thomas.stellard@amd.com>