atm: remove unused ATM PHY operations

atm: remove unused ATM PHY operations

The PHY operations are vestiges of the SAR/framer split used by the
removed PCI/SBUS ATM adapters:

 - atmdev_ops::phy_put / ::phy_get (register accessors) are never called
   by the core and solos-pci only listed them as NULL
 - struct atmphy_ops and atm_dev::phy have no users at all - nothing
   assigns or dereferences them

Remove all of them. atm_dev::phy_data is kept: solos-pci repurposes it
to stash its per-port channel index.

Link: https://patch.msgid.link/20260615194416.752559-9-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>