The new MMU setup will need SDRAM base addresses and sizes.
For this reason convert the MMU enabled ARM boards:

- move mem setup to mem_initcall. This is early but
  still makes sure that we already have the console available
- move MMU setup in this initcall temporary as after the mmu_init will generic

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>