x86_64: reserve TCEs with the same address as MEM regions

This works around a bug where DMAs that have the same addresses as
some MEM regions do not go through. Not clear yet if this is due to a
mis-configuration or something deeper.

[akpm@linux-foundation.org: coding style fixlet]
Signed-off-by: Muli Ben-Yehuda <muli@il.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>