staging: dgrp: use correct release op for /proc/dgrp/info

staging: dgrp: use correct release op for /proc/dgrp/info

Trinity (the syscall fuzzer) discovered that reading /proc/dgrp/info was
leaking some memory. Fix by using the correct release op in info_proc_file_ops.

unreferenced object 0xffff88003b6696e0 (size 32):
  comm "cat", pid 2321, jiffies 4294705179 (age 29.434s)
  hex dump (first 32 bytes):
    40 79 1c 81 ff ff ff ff 60 79 1c 81 ff ff ff ff  @y......`y......
    50 79 1c 81 ff ff ff ff b0 62 89 81 ff ff ff ff  Py.......b......
  backtrace:
    [<ffffffff81c7e3b1>] kmemleak_alloc+0x21/0x50
    [<ffffffff811955cb>] kmem_cache_alloc_trace+0x11b/0x190
    [<ffffffff811c87dc>] single_open+0x3c/0xc0
    [<ffffffff81896495>] info_proc_open+0x15/0x20
    [<ffffffff8120c6d7>] proc_reg_open+0xb7/0x160
    [<ffffffff811a1a5c>] do_dentry_open+0x1cc/0x280
    [<ffffffff811a296a>] finish_open+0x4a/0x60
    [<ffffffff811b14d7>] do_last+0xb07/0xdb0
    [<ffffffff811b1842>] path_openat+0xc2/0x4f0
    [<ffffffff811b1cac>] do_filp_open+0x3c/0xa0
    [<ffffffff811a2dcc>] do_sys_open+0x11c/0x1c0
    [<ffffffff811a2e8c>] sys_open+0x1c/0x20
    [<ffffffff81ca3d69>] system_call_fastpath+0x16/0x1b
    [<ffffffffffffffff>] 0xffffffffffffffff

Signed-off-by: Tommi Rantala <tt.rantala@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>