qcacld-3.0: Implement temporary WAR for BT coex issue

Implement a WAR to address a BT coex issue, along with a private ioctl
which can be used to switch the WAR on or off dynamically.

Change-Id: I9d29c141106db479039789d67c45a455e96a118b
CRs-Fixed: 2383150
diff --git a/Kbuild b/Kbuild
index e5d76c4..36742bb 100644
--- a/Kbuild
+++ b/Kbuild
@@ -2560,6 +2560,8 @@
 ccflags-y += -DQDF_LOCK_STATS_LIST_SIZE=256
 endif
 
+ccflags-$(CONFIG_HASTINGS_BT_WAR) += -DHASTINGS_BT_WAR
+
 KBUILD_CPPFLAGS += $(cppflags-y)
 
 # Currently, for versions of gcc which support it, the kernel Makefile