modprobe: emit "can't open 'modules.dep': (errno)" instead of "module not found"

modprobe: emit "can't open 'modules.dep': (errno)" instead of "module not found"
*: s/can't open %s/can't open '%s'/, it's better to use same string.

function                                             old     new   delta
do_modprobe                                          588     601     +13
config_file_action                                   339     345      +6
modprobe_main                                        565     570      +5
unable_to_open                                        14      16      +2
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 4/0 up/down: 26/0)               Total: 26 bytes
   text    data     bss     dec     hex filename
 816800     476    7892  825168   c9750 busybox_old
 816812     476    7892  825180   c975c busybox_unstripped