init: allow read of /sys/devices/virtual/block/zram

Commit erroneously 55039509 removed init's read access to
/sys/devices/virtual/block/zram*. Restore access.

Test: cat /proc/meminfo
    ...
    SwapTotal:        524284 kB
    SwapFree:         524284 kB
    ...
Bug: 71510938

Change-Id: I20268168caa541a7dafa1e32339641095e1e524b