crypto: octeontx2 - fix missing unlock

commit 1acf9b18d3c7b0bee35e518b2d131e1c00fe69e5 from
git@git.assembla.com:cavium/WindRiver.linux.git

Add the missing unlock before return from error path.

Fixes: 4363f3d3 ("crypto: octeontx2 - add synchronization between mailbox accesses")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Change-Id: Idf3e63005f65198511a3c63a9cce2437fb22619a
Reviewed-on: https://sj1git1.cavium.com/c/IP/SW/kernel/linux/+/90411


Tested-by: sa_ip-sw-jenkins <sa_ip-sw-jenkins@marvell.com>
Reviewed-by: Nithin Kumar Dabilpuram <ndabilpuram@marvell.com>
Reviewed-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
Signed-off-by: Beniamin Sandu <beniamin.sandu@windriver.com>