cnss: Syncronize System PM with Runtime PM

During system suspend, device resume is deffered from pm prepare
to pm suspend for devices whose children are runtime enabled
in bbb44d9f 3.18 kernel.
This results in invalid access to PCIe during system resume by
the wlan driver in the following case
Cfg80211 suspended -> runtime suspend -> cfg80211 resume(Due to
system PM failed by other device).

In cfg80211_resume, driver tries to delete the wow patterns from
FW, which are runtime tagged, hence accessing the bus results in
Clocked down bus access.

The fix should ensure our wlan device is runtime resumed before
system suspend begins.

Our wlan device has no children which are runtime controlled,
ignore_children for our device should be set.

Fix this by enabling ignore_children for wlan device to
runtime resume the PCIe child devices during pm prepare.

Change-Id: Ibf7eca6c344d427e0ac05c1bd903bab1073236a5
Signed-off-by: Komal Seelam <kseelam@codeaurora.org>
CRs-Fixed: 891485