ARM: pxa: pxa_cplds: signedness bug in probe

"base_irq" needs to be signed for the error handling to work.  Also we
can remove the initialization because we re-assign it later.

Fixes: aa8d6b73 ('ARM: pxa: pxa_cplds: add lubbock and mainstone IO')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>