s390/configs: Enable VDPA on Nvidia ConnectX-6 network card

s390/configs: Enable VDPA on Nvidia ConnectX-6 network card

ConnectX-6 is the first VDPA-capable NIC. For earlier NICs, Nvidia
implements a VDPA emulation in s/w, which hasn't been validated on s390.

Add options necessary for VDPA to work.

These options are also added because Fedora has them:
  CONFIG_VDPA_SIM
  CONFIG_VDPA_SIM_NET
  CONFIG_VDPA_SIM_BLOCK
  CONFIG_VDPA_USER
  CONFIG_VP_VDPA

Signed-off-by: Konstantin Shkolnyy <kshk@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>