and-xgbe: remove the abstraction for hwptp

Remove the hwptp abstraction and associated callbacks from
the struct xgbe_hw_if {}.

The callback structure was only ever assigned a single function, without
null checks. This cleanup inlines the logic and moves all the hwtstamp
realted code a separate file, improving readability and maintainance.

Signed-off-by: Raju Rangoju <Raju.Rangoju@amd.com>
Link: https://patch.msgid.link/20250718185628.4038779-2-Raju.Rangoju@amd.com


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