dm era: fix error code propagation in era_ctr()

dm era: fix error code propagation in era_ctr()

era_ctr() replaces the actual error codes returned by dm_get_device()
and dm_set_target_max_io_len() with hardcoded -EINVAL, discarding
the real reason for the failure (e.g. -ENODEV, -ENOMEM).  This makes
it harder for users to diagnose problems and is inconsistent with
other dm targets (dm-thin, dm-verity, dm-flakey, dm-ebs) which
propagate the original error.

Fix all three sites to return 'r' instead of -EINVAL.

Signed-off-by: Cao Guanghui <caoguanghui@kylinos.cn>
Reviewed-by: Su Yue <glass.su@suse.com>
Reviewed-by: Ming-Hung Tsai <mtsai@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>