machine: qemu: add usb host passthrough

QEMU usb-host driver which is the one for passthrough, supports two
options for selecting an USB devices in the host to provide it to the
VM:
 - Bus and Device number the device is plugged
 - Vendor and Product information of the USB devices

    https://qemu-project.gitlab.io/qemu/system/devices/usb.html

This commit allows a user to configure podman machine with either of
options, with new --usb command line option for podman machine init.

Examples
  podman machine init tosovm4 --usb vendor=13d3,product=5406
  podman machine init tosovm3 --usb bus=1,devnum=4 --usb bus=1,devnum=3

This commit also allows a user to change the USBs configured with
--usb command line option for podman machine set.

Note that this commit does not handle host device permissions nor
verify that the USB devices exists.

Signed-off-by: Victor Toso <victortoso@redhat.com>

pkg/machine/config.go

@@ -39,6 +39,7 @@ type InitOptions struct {
 	Rootful            bool
 	UID                string // uid of the user that called machine
 	UserModeNetworking *bool  // nil = use backend/system default, false = disable, true = enable
+	USBs               []string
 }
 
 type Status = string
@@ -106,6 +107,7 @@ type SetOptions struct {
 	Memory             *uint64
 	Rootful            *bool
 	UserModeNetworking *bool
+	USBs               *[]string
 }
 
 type SSHOptions struct {
@@ -271,6 +273,13 @@ func ConfDirPrefix() (string, error) {
 	return confDir, nil
 }
 
+type USBConfig struct {
+	Bus       string
+	DevNumber string
+	Vendor    int
+	Product   int
+}
+
 // ResourceConfig describes physical attributes of the machine
 type ResourceConfig struct {
 	// CPUs to be assigned to the VM
@@ -279,6 +288,8 @@ type ResourceConfig struct {
 	DiskSize uint64
 	// Memory in megabytes assigned to the vm
 	Memory uint64
+	// Usbs
+	USBs []USBConfig
 }
 
 type Mount struct {