bluetooth: Type cast the received data before parsing

On x86 platforms we observe that the data received from socket
buffer needs to be type casted to unsigned char in order to
parse the bluetooth sleep packets sent by the bluetooth
controller to APPS processor

Change-Id: If398a3b1ccf7972555fa1a53e6c117874e7b1301
Signed-off-by: Anantha Krishnan <ananthk@codeaurora.org>