It's common to set up an iovec around a single buffer; add a helper for
this.
Signed-off-by: John Levon <john.levon@nutanix.com>
Change-Id: Ic4183e29d78549ec102045c6af0b5ff448cb5c59
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/16192
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Aleksey Marchuk <alexeymar@nvidia.com>