wlan: Decode length field in the ANI msg header

PTT socket app is using ntohs conversion to fill message length in ANI
message header. But the driver is accessing this length field directly
without any conversion. Because of this the length check is failing in
the driver even for valid netlink messages.

To avoid this, decode the ani message length using be16_to_cpu.

Change-Id: I7405520867a231cf5589650f93d11629aa3f43f8
CRs-Fixed: 2860983