bnxt_en: allocate enough space for ->ntp_fltr_bmap

We have the number of longs, but we need to calculate the number of
bytes required.

Fixes: c0c050c5 ("bnxt_en: New Broadcom ethernet driver.")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>