ARM: omap2plus_defconfig: enable DP83867 phy driver

TI's DP83867 phy is used on DRA72x EVM rev C and DRA71x
EVMs. Enable support for it in omap2plus_defconfig.

The driver is built into the kernel to help NFS booting.

Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>