LU-17189 o2ib: assign tx_gpu properly

LU-17189 o2ib: assign tx_gpu properly

tx_gpu is not assigned or initialized properly.

Test-Parameters: trivial
Fixes: f792297212 ("LU-16211 o2iblnd: Avoid NULL md deref")
Signed-off-by: Jinshan Xiong <jinshan.xiong@gmail.com>
Change-Id: I5e14d66f41f6194203fec7832493efd432b54c36
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/52702
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Andrew Perepechko <andrew.perepechko@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>