tg3: Use bool not int

Using bool can make code more readable.

Convert uses and tests of int to bool.

This also makes a comparison of tg3->link_up
(itself bool) a bool comparison instead of int.

Reorder stack variable declarations to make
bool fit declaration holes where appropriate.

$ size drivers/net/ethernet/broadcom/tg3.o*
   text	   data	    bss	    dec	    hex	filename
 169958	  27249	  58896	 256103	  3e867	drivers/net/ethernet/broadcom/tg3.o.new
 169968	  27249	  58896	 256113	  3e871	drivers/net/ethernet/broadcom/tg3.o.old
Signed-off-by: Joe Perches <joe@perches.com>
Reviewed-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>