bnxt_en: Fix array overrun in bnxt_fill_l2_rewrite_fields().

Fix the array overrun while keeping the eth_addr and eth_addr_mask
pointers as u16 to avoid unaligned u16 access.  These were overlooked
when modifying the code to use u16 pointer for proper alignment.

Fixes: 90f90624

 ("bnxt_en: Add support for L2 rewrite")
Reported-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Venkat Duvvuru <venkatkumar.duvvuru@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>