tty: Fix memory leak in virtual console when enable unicode translation

tty: Fix memory leak in virtual console when enable unicode translation

Virtual console unicode translation map leaks with following
message when enable kmemleak:

unreferenced object 0xeb5ec450 (size 192):
  comm "setfont", pid 665, jiffies 4294899028 (age 3696.220s)
  hex dump (first 32 bytes):
    e0 5b 9d eb 00 00 00 00 00 00 00 00 80 b9 ea eb  .[..............
    b0 5a 9d eb 00 00 00 00 00 00 00 00 00 00 00 00  .Z..............
  backtrace:
    [<c1533f8c>] kmemleak_alloc+0x3c/0xa0
    [<c114acc2>] kmem_cache_alloc_trace+0xe2/0x250
    [<c13498e8>] con_clear_unimap+0x78/0xd0
    [<c1345552>] vt_ioctl+0x1562/0x1d00
    [<c133aa00>] tty_ioctl+0x230/0x7c0
    [<c1171519>] do_vfs_ioctl+0x79/0x2d0
    [<c11717df>] sys_ioctl+0x6f/0x80
    [<c156601f>] sysenter_do_call+0x12/0x38
    [<ffffffff>] 0xffffffff
unreferenced object 0xeb9d5be0 (size 128):
  comm "setfont", pid 660, jiffies 4294899030 (age 3696.212s)
  hex dump (first 32 bytes):
    60 c2 a6 eb 50 c8 a6 eb c0 54 9d eb 80 59 9d eb  `...P....T...Y..
    90 53 9d eb 60 52 9d eb 60 92 9b eb 00 00 00 00  .S..`R..`.......
  backtrace:
    [<c1533f8c>] kmemleak_alloc+0x3c/0xa0
    [<c114acc2>] kmem_cache_alloc_trace+0xe2/0x250
    [<c134938c>] con_insert_unipair+0x7c/0x150
    [<c1349f8c>] con_set_unimap+0x15c/0x1f0
    [<c13456fb>] vt_ioctl+0x170b/0x1d00
    [<c133aa00>] tty_ioctl+0x230/0x7c0
    [<c1171519>] do_vfs_ioctl+0x79/0x2d0
    [<c11717df>] sys_ioctl+0x6f/0x80
    [<c156601f>] sysenter_do_call+0x12/0x38
    [<ffffffff>] 0xffffffff

The leak caused by con_set_default_unimap() not correct free the old map.

Signed-off-by: Zeng Zhaoming <zengzm.kernel@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>