ARM: dts: Keystone: add ECC error handler support

Add emif node for keystone2 devices, which is used for ECC support.

Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
[t-kristo@ti.com: made emif enabled by default for all keystone2 devices]
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Acked-by: Santosh Shilimkar <ssantosh@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>