of: overlay: Remove redundant assignment to ret

Variable ret is set to zero but this value is never read as it is
overwritten with a new value later on, hence it is a redundant
assignment and can be removed.

Cleans up the following clang-analyzer warning:

drivers/of/overlay.c:1197:2: warning: Value stored to 'ret' is never
read [clang-analyzer-deadcode.DeadStores].

drivers/of/overlay.c:1026:2: warning: Value stored to 'ret' is never
read [clang-analyzer-deadcode.DeadStores].

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Link: https://lore.kernel.org/r/1619347258-55002-1-git-send-email-jiapeng.chong@linux.alibaba.com
Signed-off-by: Rob Herring <robh@kernel.org>