net: usb: smsc75xx: stop lying about skb->truesize

Some usb drivers try to set small skb->truesize and break
core networking stacks.

In this patch, I removed one of the skb->truesize override.

I also replaced one skb_clone() by an allocation of a fresh
and small skb, to get minimally sized skbs, like we did
in commit 1e2c6117 ("net: cdc_ncm: reduce skb truesize
in rx path") and 4ce62d5b ("net: usb: ax88179_178a:
stop lying about skb->truesize")

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Steve Glendinning <steve.glendinning@shawell.net>
Link: https://lore.kernel.org/r/20240506142358.3657918-1-edumazet@google.com


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