docbook: fix errors from x86 headers merger

Fix docbook errors for x86 headers that were recently merged:

docproc: arch/x86/include/asm/atomic_32.h: No such file or directory
docproc: arch/x86/include/asm/io_32.h: No such file or directory

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