zd1211rw: Use const

Mark arrays const that are unmodified after initializations.

   text	   data	    bss	    dec	    hex	filename
  19291	     56	   4136	  23483	   5bbb	drivers/net/wireless/zd1211rw/zd_chip.o.old
  19291	     56	   4136	  23483	   5bbb	drivers/net/wireless/zd1211rw/zd_chip.o.new

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>