net: macb: initialize bp->queues[0].bp for at91rm9200

The macb driver currently crashes on at91rm9200 with the following trace:

Unable to handle kernel NULL pointer dereference at virtual address 00000014
[...]
[<c031da44>] (macb_rx_desc) from [<c031f2bc>] (at91ether_open+0x2e8/0x3f8)
[<c031f2bc>] (at91ether_open) from [<c041e8d8>] (__dev_open+0x120/0x13c)
[<c041e8d8>] (__dev_open) from [<c041ec08>] (__dev_change_flags+0x17c/0x1a8)
[<c041ec08>] (__dev_change_flags) from [<c041ec4c>] (dev_change_flags+0x18/0x4c)
[<c041ec4c>] (dev_change_flags) from [<c07a5f4c>] (ip_auto_config+0x220/0x10b0)
[<c07a5f4c>] (ip_auto_config) from [<c000a4fc>] (do_one_initcall+0x78/0x18c)
[<c000a4fc>] (do_one_initcall) from [<c0783e50>] (kernel_init_freeable+0x184/0x1c4)
[<c0783e50>] (kernel_init_freeable) from [<c0574d70>] (kernel_init+0x8/0xe8)
[<c0574d70>] (kernel_init) from [<c00090e0>] (ret_from_fork+0x14/0x34)

Solve that by initializing bp->queues[0].bp in at91ether_init (as is done
in macb_init).

Fixes: ae1f2a56 ("net: macb: Added support for many RX queues")
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>