drivers: wifi: Fix missing L2 header in max MSDU calculation

MTU doesn't include any L2 overhead, so, we need to add Ethernet header
len for maximum frame size that we can received from the networking
stack.

Fixes SHEL-2214.

Signed-off-by: Chaitanya Tata <Chaitanya.Tata@nordicsemi.no>

Author: krish2718

drivers/wifi/nrf700x/src/fmac_main.c

@@ -49,7 +49,7 @@ struct nrf_wifi_drv_priv_zep rpu_drv_priv_zep;
 #define MAX_RX_QUEUES 3
 
 #define MAX_TX_FRAME_SIZE \
-	(CONFIG_NRF_WIFI_IFACE_MTU + TX_BUF_HEADROOM)
+	(CONFIG_NRF_WIFI_IFACE_MTU + NRF_WIFI_FMAC_ETH_HDR_LEN + TX_BUF_HEADROOM)
 #define TOTAL_TX_SIZE \
 	(CONFIG_NRF700X_MAX_TX_TOKENS * CONFIG_NRF700X_TX_MAX_DATA_SIZE)
 #define TOTAL_RX_SIZE \