vp_vdpa: correct the return value when fail to map notification

mainline inclusion
from mainline-v5.14-rc1
commit 94e48d6a
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5WXCZ
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=94e48d6aafef23143f92eadd010c505c49487576



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We forget to assign a error value when we fail to map the notification
during prove. This patch fixes it.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 11d8ffed ("vp_vdpa: switch to use vp_modern_map_vq_notify()")
Signed-off-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20210624035939.26618-1-jasowang@redhat.com


Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Pengyuan Zhao <zhaopengyuan@hisilicon.com>