ll_map: disable interface name caching code

ll_map: disable interface name caching code

function                                             old     new   delta
find_by_index                                          -      26     +26
static.icache                                          4       -      -4
ll_idx_n2a                                            71      59     -12
static.ncache                                         16       -     -16
ll_index_to_flags                                     40      24     -16
xll_name_to_index                                    206     104    -102
------------------------------------------------------------------------------
(add/remove: 1/2 grow/shrink: 0/3 up/down: 26/-150)          Total: -124 bytes

   text    data     bss     dec     hex filename
 734703    3040   14440  752183   b7a37 busybox_old
 734599    3040   14416  752055   b79b7 busybox_unstripped