ash: fix TMOUT not restoring tty attributes

ash: fix TMOUT not restoring tty attributes

function                                             old     new   delta
pgetc                                                420     500     +80
readtoken1                                          3202    3239     +37
read_line_input                                     3316    3337     +21
udhcpc_main                                         2610    2630     +20
file_get                                             266     272      +6
expandarg                                            958     963      +5
localcmd                                             257     259      +2
addLines                                              85      87      +2
read_line                                             94      95      +1
ed_main                                             2540    2541      +1
timed_out                                              1       -      -1
lineedit_read_key                                    256     255      -1
alrm_sighandler                                       44       -     -44
cmdloop                                              539     434    -105
------------------------------------------------------------------------------
(add/remove: 0/2 grow/shrink: 10/2 up/down: 175/-151)          Total: 24 bytes
   text    data     bss     dec     hex filename
 887379     936   17200  905515   dd12b busybox_old
 887411     936   17192  905539   dd143 busybox_unstripped

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>