add a condition for the cl_ext_image_requirements_info extension (#829)

This condition is needed to properly generate headers for this extension
because the entire extension requires OpenCL 3.0.

Author: bashbaug

xml/cl.xml

@@ -7114,7 +7114,7 @@ server's OpenCL/api-docs repository.
                 <command name="clEnqueueWriteHostPipeINTEL"/>
             </require>
         </extension>
-        <extension name="cl_ext_image_requirements_info" supported="opencl">
+        <extension name="cl_ext_image_requirements_info" condition="defined(CL_VERSION_3_0)" supported="opencl">
             <require comment="Types">
                 <type name="cl_image_requirements_info_ext"/>
             </require>