Based on:
RT5592_ChipSwitchChannel()
RT5592_Frequency_Plan_Xtal20M[]
RT5592_Frequency_Plan_Xtal40M[]

from:
DPO_RT5572_LinuxSTA_2.6.1.3_20121022/chips/rt5592.c
Signed-off-by: Stanislaw Gruszka <stf_xl@wp.pl>
Tested-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>