net: sun8i_emac: Add EPHY CLK and RESET support

Add EPHY CLK and RESET support for sun8i_emac driver to
enable EPHY TX clock and EPHY reset pins via CLK and RESET
framework.

Cc: Joe Hershberger <joe.hershberger@ni.com>
Cc: Lothar Felten <lothar.felten@gmail.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>