Add support for implementing transceiver node as phy. The max_bitrate
is obtained by getting a phy attribute.

Link: https://lore.kernel.org/r/20210724174001.553047-1-mkl@pengutronix.deSigned-off-by: Faiz Abbas <faiz_abbas@ti.com>
Signed-off-by: Aswath Govindraju <a-govindraju@ti.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>