phy: rename hwtstamp callback to hwtstamp_set

phy: rename hwtstamp callback to hwtstamp_set

PHY devices has hwtstamp callback which actually performs set operation.
Rename it to better reflect the action.

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Kory Maincent <kory.maincent@bootlin.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Link: https://patch.msgid.link/20251124181151.277256-2-vadim.fedorenko@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>