qlge: Replacing add_timer() to mod_timer()

Currently qlge driver calls add_timer() instead of mod_timer().
This patch changes add_timer() to mod_timer(), which seems a better
solution.

Signed-off-by: Breno Leitao <leitao@linux.vnet.ibm.com>
Signed-off-by: Ron Mercer <ron.mercer@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>