blockdev: code shrink

blockdev: code shrink

function                                             old     new   delta
bdcmd_names                                            -      82     +82
bdcmd_ioctl                                            -      44     +44
bdcmd_flags                                            -      11     +11
blockdev_main                                        273     258     -15
bdcommands                                           176       -    -176
------------------------------------------------------------------------------
(add/remove: 3/1 grow/shrink: 0/1 up/down: 137/-191)          Total: -54 bytes
   text	   data	    bss	    dec	    hex	filename
 982326	    485	   7296	 990107	  f1b9b	busybox_old
 982272	    485	   7296	 990053	  f1b65	busybox_unstripped

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