Hookup GRALLOC_HANDLE_HAS_CUSTOM_CONTENT_MD_RESERVED_SIZE

The gralloc struct has been conditionally adjusted not to
break blobs that use the old struct.

So far only GRALLOC_HANDLE_HAS_RESERVED_SIZE was hooked up
for Google Pixels, but it's now time to hook up the remaining flag.

Change-Id: I175bd328bd9733b9487e349f7a8486f15ef0a450