wifi: rtl8xxxu: Fix RX skb size for aggregation disabled

wifi: rtl8xxxu: Fix RX skb size for aggregation disabled

Commit 1e5b3b3fe9e0 ("rtl8xxxu: Adjust RX skb size to include space for
phystats") increased the skb size when aggregation is enabled but decreased
it for the aggregation disabled case.

As a result, if a frame near the maximum size is received,
rtl8xxxu_rx_complete() is called with status -EOVERFLOW and then the
driver starts to malfunction and no further communication is possible.

Restore the skb size in the aggregation disabled case.

Fixes: 1e5b3b3fe9e0 ("rtl8xxxu: Adjust RX skb size to include space for phystats")
Signed-off-by: Martin Kaistra <martin.kaistra@linutronix.de>
Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20250709121522.1992366-1-martin.kaistra@linutronix.de