xml: some extensions referencing promoted structs

[AlexRouSg]

While parsing the xml for code generation purposes, I noticed there are 2 extensions where the "feature" element references promoted structs rather than the EXT version. This seems unintentional as every other extension does not do this.

VK_EXT_subgroup_size_control has:

                <feature name="subgroupSizeControl" struct="VkPhysicalDeviceSubgroupSizeControlFeatures"/>
                <feature name="computeFullSubgroups" struct="VkPhysicalDeviceSubgroupSizeControlFeatures"/>

VK_EXT_pipeline_creation_cache_control has:

                <feature name="pipelineCreationCacheControl" struct="VkPhysicalDevicePipelineCreationCacheControlFeatures"/>

[oddhack]

Thanks! See #2750.