__FUNCTION__ is gcc-specific, use __func__

The change in pci-iommu,c should be safe as arena has not been assigned
when we get to this point.

Some were within #if 0 blocks, have changed them and left the blocks
as they appear to be debugging infrastructure.

A #define FN __FUNCTION__ was removed and occurances of FN were replaced
with __func__ as well.
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Richard Henderson <rth@twiddle.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>