Xenial update to 4.4.73 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 4.4.73 upstream stable
       patch set is now available. It should be included in the Ubuntu
       kernel as well.

       git://git.kernel.org/

    TEST CASE: TBD

The following patches from the 4.4.73 stable release shall be applied:
* s390/vmem: fix identity mapping
* partitions/msdos: FreeBSD UFS2 file systems are not recognized
* ARM: dts: imx6dl: Fix the VDD_ARM_CAP voltage for 396MHz operation
* staging: rtl8192e: rtl92e_fill_tx_desc fix write to mapped out memory.
* net: xilinx_emaclite: fix freezes due to unordered I/O
* net: xilinx_emaclite: fix receive buffer overflow
* ipv6: Handle IPv4-mapped src to in6addr_any dst.
* ipv6: Inhibit IPv4-mapped src address on the wire.
* NET: Fix /proc/net/arp for AX.25
* NET: mkiss: Fix panic
* net: hns: Fix the device being used for dma mapping during TX
* sierra_net: Skip validating irrelevant fields for IDLE LSIs
* sierra_net: Add support for IPv6 and Dual-Stack Link Sense Indications
* i2c: piix4: Fix request_region size
* ipv6: Fix IPv6 packet loss in scenarios involving roaming + snooping
  switches
* PM / runtime: Avoid false-positive warnings from might_sleep_if()
* jump label: pass kbuild_cflags when checking for asm goto support
* kasan: respect /proc/sys/kernel/traceoff_on_warning
* log2: make order_base_2() behave correctly on const input value zero
* ethtool: do not vzalloc(0) on registers dump
* fscache: Fix dead object requeue
* fscache: Clear outstanding writes when disabling a cookie
* FS-Cache: Initialise stores_lock in netfs cookie
* ipv6: fix flow labels when the traffic class is non-0
* drm/nouveau: prevent userspace from deleting client object
* drm/nouveau/fence/g84-: protect against concurrent access to semaphore
  buffers
* gianfar: synchronize DMA API usage by free_skb_rx_queue w/ gfar_new_page
* pinctrl: berlin-bg4ct: fix the value for "sd1a" of pin SCRD0_CRD_PRES
* net: adaptec: starfire: add checks for dma mapping errors
* parisc, parport_gsc: Fixes for printk continuation lines
* drm/nouveau: Don't enabling polling twice on runtime resume
* drm/ast: Fixed system hanged if disable P2A
* ravb: unmap descriptors when freeing rings
* nfs: Fix "Don't increment lock sequence ID after NFS4ERR_MOVED"
* r8152: re-schedule napi for tx
* r8152: fix rtl8152_post_reset function
* r8152: avoid start_xmit to schedule napi when napi is disabled
* sctp: sctp_addr_id2transport should verify the addr before looking up assoc
* romfs: use different way to generate fsid for BLOCK or MTD
* proc: add a schedule point in proc_pid_readdir()
* tipc: ignore requests when the connection state is not CONNECTED
* xtensa: don't use linux IRQ #0
* s390/kvm: do not rely on the ILC on kvm host protection fauls
* sparc64: make string buffers large enough
* Linux 4.4.73