net: ravb: Only advertise Rx/Tx timestamps if hardware supports it

net: ravb: Only advertise Rx/Tx timestamps if hardware supports it

Recent work moving the reporting of Rx software timestamps to the core
[1] highlighted an issue where hardware time stamping was advertised
for the platforms where it is not supported.

Fix this by covering advertising support for hardware timestamps only if
the hardware supports it. Due to the Tx implementation in RAVB software
Tx timestamping is also only considered if the hardware supports
hardware timestamps. This should be addressed in future, but this fix
only reflects what the driver currently implements.

1. Commit 277901ee3a26 ("ravb: Remove setting of RX software timestamp")

Fixes: 7e09a052dc4e ("ravb: Exclude gPTP feature support for RZ/G2L")
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Tested-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Link: https://patch.msgid.link/20241014124343.3875285-1-niklas.soderlund+renesas@ragnatech.se
Signed-off-by: Jakub Kicinski <kuba@kernel.org>