net: dsa: tag_brcm: let DSA core deal with TX reallocation

net: dsa: tag_brcm: let DSA core deal with TX reallocation

[ Upstream commit 2f0d030c5ffec6660f79a32b4f522155f75a9d71 ]

Now that we have a central TX reallocation procedure that accounts for
the tagger's needed headroom in a generic way, we can remove the
skb_cow_head call.

Cc: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>