tg3: Move napi_add calls below tg3_get_invariants

tg3_get_invariants(), among other things, discovers whether or not
the device is MSI-X capable and how many interrupts it supports.
This discovery needs to happen before registering NAPI instances with
netdev.  This patch moves the code block that calls napi_add later in
tg3_init_one() so that tg3_get_invariants() has a chance to run first.

Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Reviewed-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>