bc: simplify bc_parse_pushName(), do not free name in it - avoids one strdup

bc: simplify bc_parse_pushName(), do not free name in it - avoids one strdup

function                                             old     new   delta
zbc_parse_name                                       511     509      -2
zdc_parse_register                                    50      43      -7
bc_parse_pushName                                     61      39     -22
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/3 up/down: 0/-31)             Total: -31 bytes
   text	   data	    bss	    dec	    hex	filename
 982183	    485	   7296	 989964	  f1b0c	busybox_old
 982152	    485	   7296	 989933	  f1aed	busybox_unstripped

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