arm: omap: emif-common: Fix ecc address calculation

ecc_address_range registers contains the start address and end address
of the DDR address space. But the ddr driver is assuming the register
contains the start address and size of the DDR address space. Because
of this the ecc enabling is failing for the 2nd range of ecc addresses.
Fix this calculation.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>