fix asm-alpha/types.h breakage

This patch fixes the following compile error on alpha caused by
commit 3726c23d
(alpha: types: use <asm-generic/int-*.h> for the alpha architecture):

<--  snip  -->

...
  CC      arch/alpha/kernel/asm-offsets.s
In file included from include2/asm/topology.h:6,
                 from /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/topology.h:34,
                 from /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/mmzone.h:683,
                 from /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/gfp.h:4,
                 from /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/slab.h:12,
                 from /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/percpu.h:5,
                 from /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/rcupdate.h:39,
                 from /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/pid.h:4,
                 from /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/sched.h:74,
                 from /home/bunk/linux/kernel-2.6/git/linux-2.6/arch/alpha/kernel/asm-offsets.c:9:
include2/asm/machvec.h:44: error: expected declaration specifiers or '...' before 'dma_addr_t'
include2/asm/machvec.h:44: error: expected declaration specifiers or '...' before 'dma_addr_t'
In file included from /home/bunk/linux/kernel-2.6/git/linux-2.6/arch/alpha/kernel/asm-offsets.c:12:
include2/asm/io.h:94: warning: type defaults to 'int' in declaration of 'dma_addr_t'
include2/asm/io.h:94: warning: variable 'dma_addr_t' declared 'inline'
include2/asm/io.h:94: error: expected ',' or ';' before 'isa_page_to_bus'
make[2]: *** [arch/alpha/kernel/asm-offsets.s] Error 1

<--  snip  -->

Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>