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

Signed-off-by: liuhailong <liuhailong@oppo.com>
收件人: 刘海龙(DuckBuBee) <liuhailong@oppo.com>
Link: https://lore.kernel.org/r/20210618095035.32410-1-liuhailong@oppo.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>