bnxt_en: Fix up bnxt_get_rxfh_indir_size().

Fix up bnxt_get_rxfh_indir_size() to return the proper current RSS
table size for P5 chips.  Change it to non-static so that bnxt.c
can use it to get the table size.

Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>