net: mana: Fix Rx DMA datasize and skb_over_panic

mana_get_rxbuf_cfg() aligns the RX buffer's DMA datasize to be
multiple of 64. So a packet slightly bigger than mtu+14, say 1536,
can be received and cause skb_over_panic.

Sample dmesg:
[ 5325.237162] skbuff: skb_over_panic: text:ffffffffc043277a len:1536 put:1536 head:ff1100018b517000 data:ff1100018b517100 tail:0x700 end:0x6ea dev:<NULL>
[ 5325.243689] ------------[ cut here ]------------
[ 5325.245748] kernel BUG at net/core/skbuff.c:192!
[ 5325.247838] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
[ 5325.258374] RIP: 0010:skb_panic+0x4f/0x60
[ 5325.302941] Call Trace:
[ 5325.304389]  <IRQ>
[ 5325.315794]  ? skb_panic+0x4f/0x60
[ 5325.317457]  ? asm_exc_invalid_op+0x1f/0x30
[ 5325.319490]  ? skb_panic+0x4f/0x60
[ 5325.321161]  skb_put+0x4e/0x50
[ 5325.322670]  mana_poll+0x6fa/0xb50 [mana]
[ 5325.324578]  __napi_poll+0x33/0x1e0
[ 5325.326328]  net_rx_action+0x12e/0x280

As discussed internally, this alignment is not necessary. To fix
this bug, remove it from the code. So oversized packets will be
marked as CQE_RX_TRUNCATED by NIC, and dropped.

Cc: stable@vger.kernel.org
Fixes: 2fbbd712 ("net: mana: Enable RX path to handle various MTU sizes")
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Link: https://lore.kernel.org/r/1712087316-20886-1-git-send-email-haiyangz@microsoft.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>