netfilter: xtables: Add snapshot of hardidletimer target

This is a snapshot of hardifletimer netfilter target as of msm-4.4
commit 469a150b7426 ("netfilter: xtables: hardidletimer target implementation")

This patch implements a hardidletimer Xtables target that can be
used to identify when interfaces have been idle for a certain period
of time.

Timers are identified by labels and are created when a rule is set
with a new label. The rules also take a timeout value (in seconds) as
an option. If more than one rule uses the same timer label, the timer
will be restarted whenever any of the rules get a hit.

One entry for each timer is created in sysfs. This attribute contains
the timer remaining for the timer to expire. The attributes are
located under the xt_idletimer class:

/sys/class/xt_hardidletimer/timers/<label>

When the timer expires, the target module sends a sysfs notification
to the userspace, which can then decide what to do (eg. disconnect to
save power)

Compared to xt_IDLETIMER, xt_HARDIDLETIMER can send notifications when
CPU is in suspend too, to notify the timer expiry.

netfilter:Notify user space on creating sysfs file

uevent indication is required to notify the user space
on creation of sysfs file entry.
This helps in creating specific sysfs labeled entries
for newly created file which are module specific.

xt_hardidletiemr: Check for remaining expiry time

-xt_hardidletimers are getting reset with addition/
deletion of any iptable rule in any chain of raw/mangle
table.
-Check and restart the timer with remaining expiry time.

Change-Id: I55c6fb211b929dfe500edda8e7c01530f944b067
CRs-Fixed: 1078373
Acked-by: Manoj Basapathi <manojbm@qti.qualcomm.com>
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Signed-off-by: Tejaswi Tanikella <tejaswit@codeaurora.org>
Signed-off-by: Devi Sandeep Endluri V V <dendluri@codeaurora.org>