ath10k: increase rx buffer size to 2048

Before, only frames with a maximum size of 1528 bytes could be
transmitted between two 802.11s nodes.

For batman-adv for instance, which adds its own header to each frame,
we typically need an MTU of at least 1532 bytes to be able to transmit
without fragmentation.

This patch now increases the maxmimum frame size from 1528 to 1656
bytes.

Tested with two ath10k devices in 802.11s mode, as well as with
batman-adv on top of 802.11s with forwarding disabled.

Fix originally found and developed by Ben Greear.

Link: greearb/ath10k-ct#89
Link: greearb/ath10k-ct@9e5ab25
Cc: Ben Greear <[email protected]>
Signed-off-by: Linus Lüssing <[email protected]>
Signed-off-by: Kalle Valo <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

drivers/net/wireless/ath/ath10k/htt.h

@@ -2241,7 +2241,7 @@ struct htt_rx_chan_info {
  * Should be: sizeof(struct htt_host_rx_desc) + max rx MSDU size,
  * rounded up to a cache line size.
  */
-#define HTT_RX_BUF_SIZE 1920
+#define HTT_RX_BUF_SIZE 2048
 #define HTT_RX_MSDU_SIZE (HTT_RX_BUF_SIZE - (int)sizeof(struct htt_rx_desc))
 
 /* Refill a bunch of RX buffers for each refill round so that FW/HW can handle