clk: sunxi: h3: Implement EPHY CLK and RESET

EPHY CLK and RESET is available in Allwinner H3 EMAC
via mdio-mux node of internal PHY. Add the respective
clock and reset reg and bits.

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