vdpa: Use simpler version of ida allocation

mainline inclusion
from mainline-v5.11-rc1
commit 418eddef
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=418eddef050d5f6393c303a94e3173847ab85466



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vdpa doesn't have any specific need to define start and end range of the
device index.
Hence use the simper version of the ida allocator.

Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Eli Cohen <elic@nvidia.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20201112064005.349268-3-parav@nvidia.com


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