libxl: add libxl_device_pci_assignable_list_free()...

... to be used by callers of libxl_device_pci_assignable_list().

Currently there is no API for callers of libxl_device_pci_assignable_list()
to free the list. The xl function pciassignable_list() calls
libxl_device_pci_dispose() on each element of the returned list, but
libxl_pci_assignable() in libxl_pci.c does not. Neither does the implementation
of libxl_device_pci_assignable_list() call libxl_device_pci_init().

This patch adds the new API function, makes sure it is used everywhere and
also modifies libxl_device_pci_assignable_list() to initialize list
entries rather than just zeroing them.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Acked-by: Wei Liu <wl@xen.org>

tools/include/libxl.h

@@ -457,6 +457,12 @@
  */
 #define LIBXL_HAVE_DEVICE_PCI_LIST_FREE 1
 
+/*
+ * LIBXL_HAVE_DEVICE_PCI_ASSIGNABLE_LIST_FREE indicates that the
+ * libxl_device_pci_assignable_list_free() function is defined.
+ */
+#define LIBXL_HAVE_DEVICE_PCI_ASSIGNABLE_LIST_FREE 1
+
 /*
  * libxl ABI compatibility
  *
@@ -2369,6 +2375,7 @@ int libxl_device_events_handler(libxl_ctx *ctx,
 int libxl_device_pci_assignable_add(libxl_ctx *ctx, libxl_device_pci *pci, int rebind);
 int libxl_device_pci_assignable_remove(libxl_ctx *ctx, libxl_device_pci *pci, int rebind);
 libxl_device_pci *libxl_device_pci_assignable_list(libxl_ctx *ctx, int *num);
+void libxl_device_pci_assignable_list_free(libxl_device_pci *list, int num);
 
 /* CPUID handling */
 int libxl_cpuid_parse_config(libxl_cpuid_policy_list *cpuid, const char* str);