Bluetooth: Fix abuse of the preincrement operator

Fix abuse of the preincrement operator as detected when building with gcc
4.6.0:

	 CC [M]  drivers/bluetooth/hci_bcsp.o
	drivers/bluetooth/hci_bcsp.c: In function 'bcsp_prepare_pkt':
	drivers/bluetooth/hci_bcsp.c:247:20: warning: operation on 'bcsp->msgq_txseq' may be undefined

Reported-by: Justin P. Mattock <justinmattock@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Gustavo F. Padovan <padovan@profusion.mobi>
Signed-off-by: David S. Miller <davem@davemloft.net>