docbook: dmapool: fix fatal changed filename

Docbook fatal error, file was moved:
docproc: linux-2.6.24-git15/drivers/base/dmapool.c: No such file or directory

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>