AAL3/4 is an obsolete connection-oriented ATM adaptation layer that has
seen no real use since the SMDS-era hardware it was designed for (90s?).
We are only maintaining ATM support in-tree to keep PPPoATM running,
and PPPoATM runs over AAL5.
Drop the "raw" AAL3/4 transport (atm_init_aal34()) and the ATM_AAL34
cases in the connect and traffic-parameter paths. A vcc_connect() with
qos.aal == ATM_AAL34 now fails with -EPROTOTYPE.
uAPI cleanup is performed later, separately.
Link: https://patch.msgid.link/20260615194416.752559-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>