Vivid update to v3.19.8-ckt21 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 v3.19.8-ckt21 upstream stable
       patch set is now available. It should be included in the Ubuntu
       kernel as well.

       git://git.launchpad.net/~canonical-kernel/linux/+git/linux-stable-ckt

    TEST CASE: TBD

       The following patches from the v3.19.8-ckt21 stable release shall be applied:

Linux 3.19.8-ckt21
net/mlx4_en: fix spurious timestamping callbacks
cxgbi: fix uninitialized flowi6
batman-adv: Fix broadcast/ogm queue limit on a removed interface
batman-adv: Reduce refcnt of removed router when updating route
batman-adv: Check skb size before using encapsulated ETH+VLAN header
jme: Fix device PM wakeup API usage
jme: Do not enable NIC WoL functions on S0
parisc: fix a bug when syscall number of tracee is __NR_Linux_syscalls
x86/tsc: Read all ratio bits from MSR_PLATFORM_INFO
mm, cma: prevent nr_isolated_* counters from going negative
x86/sysfb_efi: Fix valid BAR address range check
MAINTAINERS: Remove asterisk from EFI directory names
drm/radeon: make sure vertical front porch is at least 1
tracing: Don't display trigger file for events that can't be enabled
Minimal fix-up of bad hashing behavior of hash_64()
powerpc: Fix bad inline asm constraint in create_zero_mask()
EDAC: i7core, sb_edac: Don't return NOTIFY_BAD from mce_decoder callback
mm: vmscan: reclaim highmem zone if buffer_heads is over limit
mm/huge_memory: replace VM_NO_THP VM_BUG_ON with actual VMA check
IB/security: Restrict use of the write() interface
ARM: SoCFPGA: Fix secondary CPU startup in thumb2 kernel
drm/i915/ddi: Fix eDP VDD handling during booting and suspend/resume
drm/i915: Fix system resume if PCI device remained enabled
cxl: Keep IRQ mappings on context teardown
drm/dp/mst: Get validated port ref in drm_dp_update_payload_part1()
workqueue: fix ghost PENDING flag while doing MQ IO
ALSA: hda - Add dock support for ThinkPad X260
USB: serial: cp210x: add Straizona Focusers device ids
USB: serial: cp210x: add ID for Link ECU
efi: Fix out-of-bounds read in variable_matches()
i2c: exynos5: Fix possible ABBA deadlock by keeping I2C clock prepared
i2c: cpm: Fix build break due to incompatible pointer types
iio: ak8975: Fix NULL pointer exception on early interrupt
ASoC: dapm: Make sure we have a card when displaying component widgets
ASoC: rt5640: Correct the digital interface data select
[3.19-stable-only] fix backport "KVM: s390: avoid memory overwrites on emergency signal injection"