Xenial update: 4.4.219 upstream stable release

SRU Justification

    Impact:
       The upstream process for stable tree updates is quite similar
       in scope to the Ubuntu SRU process, e.g., each patch has to
       demonstrably fix a bug, and each patch is vetted by upstream
       by originating either directly from a mainline/stable Linux tree or
       a minimally backported form of that patch. The following upstream
       stable patches should be included in the Ubuntu kernel:

       4.4.219 upstream stable release
       from git://git.kernel.org/

The following patches from the 4.4.219 stable release shall be applied:
* drm/bochs: downgrade pci_request_region failure from error to warning
* ipv4: fix a RCU-list lock in fib_triestat_seq_show
* net, ip_tunnel: fix interface lookup with no key
* sctp: fix possibly using a bad saddr with a given dst
* l2tp: Correctly return -EBADF from pppol2tp_getname.
* net: l2tp: Make l2tp_ip6 namespace aware
* l2tp: fix race in l2tp_recv_common()
* l2tp: ensure session can't get removed during pppol2tp_session_ioctl()
* l2tp: fix duplicate session creation
* l2tp: Refactor the codes with existing macros instead of literal number
* l2tp: ensure sessions are freed after their PPPOL2TP socket
* l2tp: fix race between l2tp_session_delete() and l2tp_tunnel_closeall()
* usb: gadget: uac2: Drop unused device qualifier descriptor
* usb: gadget: printer: Drop unused device qualifier descriptor
* padata: always acquire cpu_hotplug_lock before pinst->lock
* mm: mempolicy: require at least one nodeid for MPOL_PREFERRED
* net: stmmac: dwmac1000: fix out-of-bounds mac address reg setting
* slcan: Don't transmit uninitialized stack data in padding
* random: always use batched entropy for get_random_u{32,64}
* tools/accounting/getdelays.c: fix netlink attribute length
* power: supply: axp288_charger: Fix unchecked return value
* xen-netfront: Fix mismatched rtnl_unlock
* xen-netfront: Update features after registering netdev
* ASoC: jz4740-i2s: Fix divider written at incorrect offset in register
* IB/hfi1: Call kobject_put() when kobject_init_and_add() fails
* Bluetooth: RFCOMM: fix ODEBUG bug in rfcomm_dev_ioctl
* RDMA/cm: Update num_paths in cma_resolve_iboe_route error flow
* clk: qcom: rcg: Return failure for RCG update
* drm_dp_mst_topology: fix broken drm_dp_sideband_parse_remote_dpcd_read()
* Linux 4.4.219