net: phy: broadcom: Add PTP support for some Broadcom PHYs.

This adds PTP support for BCM54210E Broadcom PHYs, in particular,
the BCM54213PE, as used in the Rasperry PI CM4.  It has only been
tested on that hardware.

Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>