Fix 44x early serial debugging for big RAM configurations (more than 512M).
 We cannot use default OpenBIOS virtual mapping, because it interferes with
pinned TLB entry.

While we are at it, move early UART mapping to TLB slot 0, so it can
survive longer during boot process (slot 1 is used by the first ioremap
call, effectively killing UART mapping if it occupies this slot).  Also,
change UART TLB entry size to 4K (256M is too much for a bunch of registers
:).  Squash some warnings on the way.

Tested on Ebony and Ocotea with 1G of RAM.

Thanks to Scott Coulter <scott.coulter@cyclone.com> for diagnosing this
problem.
Signed-off-by: NEugene Surovegin <ebs@ebshome.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>