io: define stronger ordering for the default writeX() implementation
The default implementation of mapping writeX() to __raw_writeX() is wrong.
writeX() has stronger ordering semantics. Compiler is allowed to reorder
memory writes against __raw_writeX().
Use the previously defined __io_aw() and __io_bw() macros to harden
code generation according to architecture support.
Signed-off-by: Sinan Kaya <okaya@codeaurora.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de>