Porting base-hw to i.mx53

[Timur]

I want to add support of i.mx53 to base-hw. I encounter a problem while 
turning on MMU. Problem appears when i want to write a system control register 
with setted mmu bit in enable_mmu function :

   Sctlr::access_t sctlr = Sctlr::read();
   Sctlr::M::set(sctlr);
   Sctlr::I::clear(sctlr);
   Sctlr::C::clear(sctlr);
-->Sctlr::write(sctlr);

after this string system freezes. 

Registers which are used in this function are the same as in Cortex A9. 

-- 
Galiullin Timur