fs/squashfs: Ensure memory is freed by using unwind goto

fs/squashfs: Ensure memory is freed by using unwind goto

Returning immediately from sqfs_read_nest is not consistent with other
error checks in this function and can lead to memory leaks. Instead use
the unwind goto used elsewhere to ensure that the memory is freed.

This issue was found by Smatch.

Signed-off-by: Andrew Goodbody <andrew.goodbody@linaro.org>
Acked-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Joao Marcos Costa <joaomarcos.costa@bootlin.com>