fs/squashfs: sqfs_probe: use sqfs_decompressor_init() return value

fs/squashfs: sqfs_probe: use sqfs_decompressor_init() return value

sqfs_decompressor_init() returns a value, so it's better to use it than
to force the return value to EINVAL (it could be ENOMEM)

Reviewed-by: Joao Marcos Costa <jmcosta944@gmail.com>
Signed-off-by: Richard Genoud <richard.genoud@posteo.net>
[jh80.chung: cherry picked from mainline commit 6d25bd3e9c1d317cdbd52a4c6bba11f912bb4d6a]
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Change-Id: I7fcad9cd4d7ecb4aff6aa353aee78c7aac69a0e6