ls: handle all sort options through option_mask32

ls: handle all sort options through option_mask32

function                                             old     new   delta
packed_usage                                       31007   31024     +17
my_stat                                              318     324      +6
sort_and_display_files                               419     420      +1
print_name                                           216     217      +1
sortcmp                                              228     216     -12
opt_flags                                             96      64     -32
ls_main                                              732     685     -47
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(add/remove: 0/0 grow/shrink: 4/3 up/down: 25/-91)            Total: -66 bytes

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