mtd: maps: ceiva: do not return random numbers

When machine_is_ceiva() returns zero, 'clps_setup_flash()' returns a
value of an unitialized variable. Fix this.

Spotted by David Binderman.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>