FROMLIST: staging: android: ashmem: add size field in procfs fdinfo

add this information to help user to find ashmem problem.

ashmem leak scenario:
-000|fd = ashmem_create_region
-001|mmap and pagefault
-002|munmap
-003|forget close(fd) <---- which lead to ashmem leak

Link: https://lore.kernel.org/patchwork/patch/1448571


Bug: 191291741
Signed-off-by: liuhailong <liuhailong@oppo.com>
Signed-off-by: xieliujie <xieliujie@oppo.com>
Change-Id: I68ac5a42357eff11056c9ed1207da07fefbea77d