LU-6142 osc: tidy up osc_init()

LU-6142 osc: tidy up osc_init()

A module_init() function that registers the services
of the module should do that last, after all other
initialization has succeeded.
This patch moves the class_register_type() call to the
end and ensures everything else that might have been
set up, is cleaned up on error.

Linux-commit: e67f133d02e ("staging: lustre: osc: tidy up osc_init()")

Lustre-change: https://review.whamcloud.com/49458
Lustre-commit: f66b0c3b22bfcf0d7ac9383df5d87317f831a03d

Change-Id: I2a5ffb116c6d7c33a4530bab6e89a5ffe6117cea
Signed-off-by: Mr. NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/54322
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>