mtd: ofpart: Fix incorrect NULL check in parse_ofoldpart_partitions()

mtd: ofpart: Fix incorrect NULL check in parse_ofoldpart_partitions()

commit 5a6ea4af0907f995dc06df21a9c9ef764c7cd3bc upstream.

The pointer returned by kzalloc should be tested for NULL
to avoid potential NULL pointer dereference later. Incorrect
pointer was being tested for NULL. Bug introduced by commit fbcf62a3
(mtd: physmap_of: move parse_obsolete_partitions to become separate
parser).
This patch fixes this bug.

Cc: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: Artem Bityutskiy <artem.bityutskiy@intel.com>
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>