sky2: Use 32bit read to read Y2_VAUX_AVAIL

B0_CTST is a 24bit register according to the vendor driver (sk98lin).
A 16bit read on B0_CTST will always return 0 for Y2_VAUX_AVAIL (1<<16),
 so use a 32bit read when testing Y2_VAUX_AVAIL

Signed-off-by: Mike McCormack <mikem@ring3k.org>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>