[ARM] 4832/2: Support AC97CLK on PXA3xx via the clock API

The AC97 clock rate on PXA3xx is generated with a configurable divider
from sys_pll.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: eric miao <eric.miao@marvell.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>