qcacmn: fix compile error in APPs when include wlan_nlink_common.h

wlan_nlink_common.h include linux/if.h, and linux/if.h
refers to 'struct sockaddr' which is defined in
linux/socket.h, and so it include linux/socket.h;
however, in userspace, linux/socket.h doesn't define
'sockaddr', so it will cause errors when compiling
userspace APP if it includs wlan_nlink_common.h.

Add macro __KERNEL__ to determine which header file
should be included:
For userspace, include net/if.h, it will include
sys/socket.h, which is for userspace;
for kernel space, include linux/if.h.

Change-Id: I3a2d8e6edb42871aa3599ef30fbb5d0d275764df
CRs-Fixed: 2054409

utils/nlink/inc/wlan_nlink_common.h

@@ -38,8 +38,12 @@
 #define WLAN_NLINK_COMMON_H__
 
 #include <linux/netlink.h>
-#include <linux/if.h>
 
+#ifdef __KERNEL__
+#include <linux/if.h>
+#else
+#include <net/if.h>
+#endif
 
 /*---------------------------------------------------------------------------
  * External Functions