wlan: Remove palPktFree in assoc request api

In the API limSendAssocReqMgmtFrame, the host
allocates memory for the assoc request packet
taking all inputs of payload and the mac header
size etc, and in case the mem allocation fails
it clears away the memory allocated to the packet
with palPktFree, which was not even allocated

Fix is to remove the packet free in case of memory not
allocated

Change-Id: I3fb75b1947dfe039605c42aa19c2d0bacc7bf55d
CRs-Fixed: 2280194