tg3: Move TG3_FLG2_PROTECTED_NVRAM to tg3_flags3

We need room for another TSO flag and it would be most efficient if it
resided in tg3_flags2.  This patch moves the TG3_FLG2_PROTECTED_NVRAM
to tg3_flags3 to make room.

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