fix typo in arch/parisc/hpux/fs.c

fix typo in arch/parisc/hpux/fs.c

A parisc allmodconfig build produces this:

arch/parisc/hpux/fs.c:107: error: 'buffer' undeclared (first use in this function)

Introduced by commit 91f49d77aec3600a8163e6ddf4ed35d434fc8444 ("[PATCH]
fix hpux_getdents()").

Helge Dille also reported this in bugzilla 11461:

	http://bugzilla.kernel.org/show_bug.cgi?id=11461

and he posted an identical patch.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>