[TCP]: Make snd_cwnd_clamp a u32.

 	u32	snd_ssthresh;	/* Slow start size threshold		*/

 	u32	snd_cwnd;	/* Sending congestion window		*/

 	u16	snd_cwnd_cnt;	/* Linear increase counter		*/

	u16	snd_cwnd_clamp; /* Do not allow snd_cwnd to grow above this */

	u32	snd_cwnd_clamp; /* Do not allow snd_cwnd to grow above this */

	u32	snd_cwnd_used;

	u32	snd_cwnd_stamp;