ARM: dts: keystone-k2e: fix mdio io start address

The K2E MDIO io space has different start address.
Hence, fix it to be 0x24200f00 according to TRM.

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>