net: usb: smsc75xx: Move packet length check to prevent kernel panic in skb_pull

[ Upstream commit 43ffe6ca ]

Packet length check needs to be located after size and align_count
calculation to prevent kernel panic in skb_pull() in case
rx_cmd_a & RX_CMD_A_RED evaluates to true.

Fixes: d8b22831

 ("net: usb: smsc75xx: Limit packet length to skb->len")
Signed-off-by: Szymon Heidrich <szymon.heidrich@gmail.com>
Link: https://lore.kernel.org/r/20230316110540.77531-1-szymon.heidrich@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>