rt2x00: make const array glrt_table static

Don't populate array glrt_table on the stack but make it static.
Makes the object code a smaller by over 670 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
 131772	   4733	      0	 136505	  21539	rt2800lib.o

After:
   text	   data	    bss	    dec	    hex	filename
 131043	   4789	      0	 135832	  21298	rt2800lib.o

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>