ARM: socfpga: dts: Add ethernet bindings for SOCFPGA

Add entry for 2nd GMAC controller. Add the correct clocks for the GMAC.

Signed-off-by: Dinh Nguyen <dinguyen@altera.com>
Reviewed-by: Pavel Machek <pavel@denx.de>
CC: Arnd Bergmann <arnd@arndb.de>
CC: Olof Johansson <olof@lixom.net>
Cc: Pavel Machek <pavel@denx.de>
CC: <linux@arm.linux.org.uk>

v2:
- Moved "disabled" status to dtsi file
Signed-off-by: Olof Johansson <olof@lixom.net>