ARM: dts: dra72: add rev C evm support

Add DTS support for dra72 evm Rev C which has the following
changes
* Two ethernet ports now instead of the single one in rev B.
* DP83867 ethernet phy instead of DP838865.

Cc: Vignesh R <vigneshr@ti.com>
Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>