parisc: Provide __ucmpdi2 to resolve undefined references in 32 bit builds.

parisc: Provide __ucmpdi2 to resolve undefined references in 32 bit builds.

The Debian experimental linux source package (3.8.5-1) build fails
with the following errors:
...
MODPOST 2016 modules
ERROR: "__ucmpdi2" [fs/btrfs/btrfs.ko] undefined!
ERROR: "__ucmpdi2" [drivers/md/dm-verity.ko] undefined!

The attached patch resolves this problem.  It is based on the s390
implementation of ucmpdi2.c.

Signed-off-by: John David Anglin <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Signed-off-by: Helge Deller <[email protected]>