LU-18893 lnet: Use negative errno for ERR_PTR

LU-18893 lnet: Use negative errno for ERR_PTR

request_module() can return a positive value from modprobe. If this
happens then we need to provide a negative errno for ERR_PTR().

Test-Parameters: trivial testlist=sanity-lnet
Fixes: 6e76d3569b ("LU-12511 lnet: rework lnd module loading ")
Signed-off-by: Chris Horn <chris.horn@hpe.com>
Change-Id: I400aa5b350fe274d18c2edb38479bb428907efb6
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58669
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Reviewed-by: Cyril Bordage <cbordage@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>